Only include unistd.h on systems which have it
Rename UUID to AUDIOFILE_UUID

Avoids name conflict with internal UUID struct in Win32.
Rename enum to avoid name conflict in Win32 API
Visual Studio compiler doesn't like this inline syntax
Fix Visual Studio compiler nag
Rename file to avoid internal name conflict

The modules subdirectory also has a g711.c, and since Visual Studio uses a
single directory for all intermediate files, this can cause linker errors.
Rename file to avoid linker error

The modules subdirectory also has a PCM.c and since Visual Studio uses a
single directory for all intermediate files, this can cause linker errors.