cmake: fix gethostby{addr,name}_r in CurlTests

This patch cleans up the automatically-generated (?) code and fixes one
case that will always fail due to syntax error.

HAVE_GETHOSTBYADDR_R_5_REENTRANT always failed because of a trailing
character ("int length;q"). Several parameter type and unused variable
warnings popped up. This causes a detection failure with -Werror.

Observe that the REENTRANT cases are exactly the same as their
non-REENTRANT cases except for a `_REENTRANT` macro definition.
Merge all these pieces and build one big main function with different
cases, but reusing variables where logical.

For the cases where the parameters where NULL, I looked at
lib/hostip4.c to get an idea of the parameters types.

void-cast variables such as 'rc' to avoid -Wuninitialized errors.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
cmake: clean OtherTests, fixing -Werror

There were several -Wunused warnings and one duplicate macro definition.
The EXTRA_DEFINES variable of the CurlCheckCSources macro was being
abused ("__unused1\n#undef inline\n#define __unused2", seriously?) to
insert extra C code. Avoid this broken abstraction and use cmake's
check_c_source_compiles directly (works fine with CMake 2.8, maybe
even cmake 2.6).

After cleaning up all related variables (EXTRA_DEFINES,
HEADER_INCLUDES, auxiliary headers_hack), also remove a duplicate
add_headers_include macro and remove duplicate header additions before
the struct timeval check.

Oh, and now the code is converted to use CheckCSourceRuns and
CheckCSourceCompiles, the two curl-specific helpers can be removed.
Unfortunately, the cmake output is now slightly more verbose. Before:

    Performing Test int send(int, const void *, size_t, int) (curl_cv_func_send_test)
    Performing Test int send(int, const void *, size_t, int) (curl_cv_func_send_test) - Failed

Since check_c_source_compiles prints the varname, now you see:

    Performing Test curl_cv_func_send_test
    Performing Test curl_cv_func_send_test - Failed
    Tested: int send(int, const void *, size_t, int)

Compared cmake output with each other using vimdiff, no functional
differences were found. Tested with GCC 4.9.1 and Clang 3.5.0.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
cmake: fix struct sockaddr_storage check

CHECK_TYPE_SIZE_PREINCLUDE is an internal, undocumented variable which
was removed in cmake 2.8.1. According to the MSDN docs[1], inclusion
of winsock2.h is sufficient. WIN32_LEAN_AND_MEAN does not really seem
to affect the tests, so remove it too[2].

For the non-windows case, remove inet headers as POSIX only requires
sys/socket.h.

 [1]: http://msdn.microsoft.com/en-us/library/windows/desktop/ms740504%28v=vs.85%29.aspx
 [2]: http://stackoverflow.com/questions/11040133/what-does-defining-win32-lean-and-mean-exclude-exactly

Signed-off-by: Peter Wu <peter@lekensteyn.nl>