btrfs-progs: Fix parallel build

Upstream-Status: Pending

"make btrfs.o" fails unable to find version.h.

This adds version.h as a dependency for all .o files and fixes various parallel 
build failures.

RP 20/9/2013
---
 Makefile |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: git/Makefile
===================================================================
--- git.orig/Makefile	2013-09-20 14:45:34.307723221 +0000
+++ git/Makefile	2013-09-20 16:06:45.503611030 +0000
@@ -76,7 +76,7 @@
 	check = true
 endif
 
-.c.o:
+%.o: %.c version.h
 	$(Q)$(check) $<
 	@echo "    [CC]     $@"
 	$(Q)$(CC) $(DEPFLAGS) $(AM_CFLAGS) $(CFLAGS) -c $<