try to merge btrfs 3.14.1

Conflicts:
	src/btrfs/disk-io.c
merger btrfs to 3.14 and update makefile

Conflicts:
	Makefile.in
	aclocal.m4
	configure
	docs/Makefile.in
	src/Makefile.in
	src/version.h
	tests/Makefile
	tests/Makefile.in