libsmbclient uses dynamically linked libtalloc.so which has symbols
with names matching those in the internal talloc.c. This name
collision caused a crash under stream_smb when trying to play
anything with smb://. Add a "#pragma GCC visibility" hack to talloc.h
to hide the internal symbols from being visible to the outside
libtalloc.so. Hopefully this doesn't break any platform worse than
possibly causing a compiler warning about an unknown pragma (at least
GCC and clang recognize it).