Tidy logic for WIN32 "%zu" checking.
Tidy logic for WIN32 "%zu" checking.

Re-arrange the logic to be a little less convoluted, and add comments explaining why it's done that way.
librsync/librsync,sourcefrog/librsync,dbaarda/librsync,sourcefrog/librsync,dbaarda/librsync,librsync/librsync,sourcefrog/librsync,librsync/librsync,dbaarda/librsync,dbaarda/librsync,sourcefrog/librsync,librsync/librsync