lib-fs-resize: add wrappers for open,close,resize,get_resize_constraint

lib-fs-resize: add wrappers for open,close,resize,get_resize_constraint

* libparted/fs/r/filesys.c: Implement ped_file_system_resize,
ped_file_system_open, ped_file_system_close and
ped_file_system_get_resize_constraint.
* libparted/fs/r/hfs/hfs.c: Give a few functions global scope,
so we can use them from the above.
* libparted/fs/Makefile.am: Use automake's subdir-objects option.
This avoids conflicts with multiple *.o file names
(e.g., fat.o), now that two directories provide that name.
(AM_CFLAGS): Disable $(WERROR_CFLAGS), for now.