endian: check byte order on OSX

Defines CEPH_[BIG|LITTLE]_ENDIAN to use, as BYTE_ORDER etc macros may be
different names on different platforms.

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
inttypes: detect and define missing integer types

Working around missing integer types is pretty easy. For example, the
__u32 family are Linux-specific types, and using these in Ceph
internally is fine because we can typedef them.

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
Merge pull request #1035 from ceph/port/bitsandints

endianess and integer types

Reviewed-by: Sage Weil <sage@inktank.com>