Include <linux/falloc.h> in bits/fcntl-linux.h.

This patch makes bits/fcntl-linux.h include <linux/falloc.h> to define
the FALLOC_* flags under __USE_GNU (linux/falloc.h defines only those
bits, nothing else).

Tested for x86_64 and x86.

	* sysdeps/unix/sysv/linux/bits/fcntl-linux.h [__USE_GNU]: Include
	<linux/falloc.h>.
	(FALLOC_FL_KEEP_SIZE): Remove.
	(FALLOC_FL_PUNCH_HOLE): Likewise.
	(FALLOC_FL_COLLAPSE_RANGE): Likewise.
	(FALLOC_FL_ZERO_RANGE): Likewise.