Add a comment to CMakeLists.txt explaining HAVE_PRINTF_Z check.
Add a comment to CMakeLists.txt explaining HAVE_PRINTF_Z check.

librsync/librsync,dbaarda/librsync,sourcefrog/librsync,sourcefrog/librsync,dbaarda/librsync,dbaarda/librsync,librsync/librsync,librsync/librsync,sourcefrog/librsync,dbaarda/librsync,sourcefrog/librsync,librsync/librsync