Implement decoding of fallocate FALLOC_FL_* flags

* xlat/falloc_flags.in: New file.
* configure.ac (AC_CHECK_HEADERS): Add linux/falloc.h.
* fallocate.c [HAVE_LINUX_FALLOC_H]: Include <linux/falloc.h>.
Include xlat/falloc_flags.h.
(sys_fallocate): Decode flags.
diff --git a/configure.ac b/configure.ac
index 8dba8af..fbd8a83 100644
--- a/configure.ac
+++ b/configure.ac
@@ -232,6 +232,7 @@
 	elf.h
 	inttypes.h
 	ioctls.h
+	linux/falloc.h
 	linux/perf_event.h
 	linux/ptrace.h
 	linux/utsname.h