Turn on USE_ST_TIMESPEC for OpenBSD

Like Darwin, OpenBSD's stat struct uses st_ctimespec and st_mtimestruct
rather than st_ctim and st_mtim.

Signed-off-by: Tony Kemp <tony.kemp@newcastle.edu.au>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -749,6 +749,7 @@ endif
 ifeq ($(uname_S),OpenBSD)
 	NO_STRCASESTR = YesPlease
 	NO_MEMMEM = YesPlease
+	USE_ST_TIMESPEC = YesPlease
 	NEEDS_LIBICONV = YesPlease
 	BASIC_CFLAGS += -I/usr/local/include
 	BASIC_LDFLAGS += -L/usr/local/lib