atomic: cleanup atomics handling and add fallbacks using a mutex.
macros: add fallback for MIN and MAX where typeof does not exist.
build: add bson-atomic.c to build
clock: handle no struct timezone on Sun C compiler.
build: add Sun C Compiler to list of compilers (__SUNPRO_C).
build: check for Glibc 2.19 to handle _BSD_SOURCE vs _GNU_SOURCE