Add support for the "strictatime" mount option.

Upstream-Status: Backport [9ad8979ff15e1b894ee1f4bb6a2535a1a2c20d65]
Signed-off-by: Ross Burton <ross.burton@intel.com>

Index: busybox-1.20.2/util-linux/mount.c
===================================================================
--- busybox-1.20.2.orig/util-linux/mount.c	2012-07-02 15:08:25.000000000 +0100
+++ busybox-1.20.2/util-linux/mount.c	2013-03-22 15:37:31.340277463 +0000
@@ -113,6 +113,12 @@
 #ifndef MS_RELATIME
 # define MS_RELATIME    (1 << 21)
 #endif
+#ifndef MS_STRICTATIME
+# define MS_STRICTATIME (1 << 24)
+#endif
+
+/* Any ~MS_FOO value has this bit set: */
+#define BB_MS_INVERTED_VALUE (1u << 31)
 
 #include "libbb.h"
 #if ENABLE_FEATURE_MOUNT_LABEL
@@ -239,6 +245,7 @@
 		/* "nomand"      */ ~MS_MANDLOCK,
 		/* "relatime"    */ MS_RELATIME,
 		/* "norelatime"  */ ~MS_RELATIME,
+		/* "strictatime" */ MS_STRICTATIME,
 		/* "loud"        */ ~MS_SILENT,
 		/* "rbind"       */ MS_BIND|MS_RECURSIVE,
 
@@ -295,6 +302,7 @@
 		"nomand\0"
 		"relatime\0"
 		"norelatime\0"
+		"strictatime\0"
 		"loud\0"
 		"rbind\0"
 
@@ -466,8 +474,8 @@
 		// Find this option in mount_options
 		for (i = 0; i < ARRAY_SIZE(mount_options); i++) {
 			if (strcasecmp(option_str, options) == 0) {
-				long fl = mount_options[i];
-				if (fl < 0)
+				unsigned long fl = mount_options[i];
+				if (fl & BB_MS_INVERTED_VALUE)
 					flags &= fl;
 				else
 					flags |= fl;