Properly fill exec_prefix in libsodium.pc, spotted by Jonas Termansen
librt and libm are not needed any more.
Thanks to Raúl Sánchez Siles for the heads up.
Do not export crypto_onetimeauth_pick_best_implementation()
Thanks Jason McCampbell for the Go bindings
Clarify what sodium_memcmp() is for.
MSVC: Don't define NDEBUG even for Release builds.
Check for Windows-specific functions by checking _WIN32, not HAVE_* definitions
MSVC: Define NATIVE_LITTLE_ENDIAN / inline as __inline / UNICODE & _UNICODE
Enable Coverity+Travis