Rename htonll/ntohll so zmqpp can build in Yosemite.

Renamed the htonll and ntohll functions because of build errors when running make. Yosemite includes its own 'htonll' and 'ntohll' functions that clash; this fix simply renames the zmqpp-defined functions.

Another workaround would be to implement a guard checking if these functions are already defined.

In file included from /Users/crh/tmp/zmqpp/src/zmqpp/message.cpp:10:
/Users/crh/tmp/zmqpp/src/zmqpp/inet.hpp:79:17: error: expected ')'
inline uint64_t htonll(uint64_t const hostlonglong)
                ^
/usr/include/sys/_endian.h:141:25: note: expanded from macro 'htonll'
#define htonll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:30: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
                             ^
/Users/crh/tmp/zmqpp/src/zmqpp/inet.hpp:79:17: note: to match this '('
/usr/include/sys/_endian.h:141:25: note: expanded from macro 'htonll'
#define htonll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:5: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
    ^
In file included from /Users/crh/tmp/zmqpp/src/zmqpp/message.cpp:10:
/Users/crh/tmp/zmqpp/src/zmqpp/inet.hpp:92:17: error: expected ')'
inline uint64_t ntohll(uint64_t const networklonglong)
                ^
/usr/include/sys/_endian.h:140:25: note: expanded from macro 'ntohll'
#define ntohll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:30: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
                             ^
/Users/crh/tmp/zmqpp/src/zmqpp/inet.hpp:92:17: note: to match this '('
/usr/include/sys/_endian.h:140:25: note: expanded from macro 'ntohll'
#define ntohll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:5: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
    ^
In file included from /Users/crh/tmp/zmqpp/src/zmqpp/message.cpp:10:
/Users/crh/tmp/zmqpp/src/zmqpp/inet.hpp:92:17: error: redefinition of '__builtin_constant_p'
inline uint64_t ntohll(uint64_t const networklonglong)
                ^
/usr/include/sys/_endian.h:140:25: note: expanded from macro 'ntohll'
#define ntohll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:6: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
     ^
/Users/crh/tmp/zmqpp/src/zmqpp/inet.hpp:79:17: note: previous definition is here
inline uint64_t htonll(uint64_t const hostlonglong)
                ^
/usr/include/sys/_endian.h:141:25: note: expanded from macro 'htonll'
#define htonll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:6: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
     ^
In file included from /Users/crh/tmp/zmqpp/src/zmqpp/message.cpp:10:
/Users/crh/tmp/zmqpp/src/zmqpp/inet.hpp:145:16: error: unexpected parenthesis after '::'
        temp = zmqpp::htonll(temp);
                      ^
/usr/include/sys/_endian.h:141:25: note: expanded from macro 'htonll'
#define htonll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:5: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
    ^
In file included from /Users/crh/tmp/zmqpp/src/zmqpp/message.cpp:10:
/Users/crh/tmp/zmqpp/src/zmqpp/inet.hpp:163:16: error: unexpected parenthesis after '::'
        temp = zmqpp::ntohll(temp);
                      ^
/usr/include/sys/_endian.h:140:25: note: expanded from macro 'ntohll'
#define ntohll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:5: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
    ^
/Users/crh/tmp/zmqpp/src/zmqpp/message.cpp:141:40: error: unexpected parenthesis after '::'
        integer = static_cast<int64_t>(zmqpp::htonll(*network_order));
                                              ^
/usr/include/sys/_endian.h:141:25: note: expanded from macro 'htonll'
#define htonll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:5: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
    ^
/Users/crh/tmp/zmqpp/src/zmqpp/message.cpp:182:28: error: unexpected parenthesis after '::'
        unsigned_integer = zmqpp::ntohll(*network_order);
                                  ^
/usr/include/sys/_endian.h:140:25: note: expanded from macro 'ntohll'
#define ntohll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:5: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
    ^
/Users/crh/tmp/zmqpp/src/zmqpp/message.cpp:240:34: error: unexpected parenthesis after '::'
        uint64_t network_order = zmqpp::htonll(static_cast<uint64_t>(integer));
                                        ^
/usr/include/sys/_endian.h:141:25: note: expanded from macro 'htonll'
#define htonll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:5: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
    ^
/Users/crh/tmp/zmqpp/src/zmqpp/message.cpp:275:34: error: unexpected parenthesis after '::'
        uint64_t network_order = zmqpp::htonll(unsigned_integer);
                                        ^
/usr/include/sys/_endian.h:141:25: note: expanded from macro 'htonll'
#define htonll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:5: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
    ^
/Users/crh/tmp/zmqpp/src/zmqpp/message.cpp:345:34: error: unexpected parenthesis after '::'
        uint64_t network_order = zmqpp::htonll(static_cast<uint64_t>(integer));
                                        ^
/usr/include/sys/_endian.h:141:25: note: expanded from macro 'htonll'
#define htonll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:5: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
    ^
/Users/crh/tmp/zmqpp/src/zmqpp/message.cpp:373:34: error: unexpected parenthesis after '::'
        uint64_t network_order = zmqpp::htonll(unsigned_integer);
                                        ^
/usr/include/sys/_endian.h:141:25: note: expanded from macro 'htonll'
#define htonll(x)       __DARWIN_OSSwapInt64(x)
                        ^
/usr/include/libkern/_OSByteOrder.h:78:5: note: expanded from macro '__DARWIN_OSSwapInt64'
    (__builtin_constant_p(x) ? __DARWIN_OSSwapConstInt64(x) : _OSSwapInt64(x))
    ^
11 errors generated.