base-files: properly escape strings for version info

Make sure they don't break the sed command, and also make device_info
and openwrt_release more robust for parsing by scripts

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 41885

package/base-files/files/etc/openwrt_release

@@ -1,7 +1,7 @@
-DISTRIB_ID="%D"
-DISTRIB_RELEASE="%C"
-DISTRIB_REVISION="%R"
-DISTRIB_CODENAME="%n"
-DISTRIB_TARGET="%S"
-DISTRIB_DESCRIPTION="%D %N %V"
-DISTRIB_TAINTS="%t"
+DISTRIB_ID='%D'
+DISTRIB_RELEASE='%C'
+DISTRIB_REVISION='%R'
+DISTRIB_CODENAME='%n'
+DISTRIB_TARGET='%S'
+DISTRIB_DESCRIPTION='%D %N %V'
+DISTRIB_TAINTS='%t'