Support alternative .android_secure location

Some devices (jewel, m8) have .android_secure at a non-standard
location. Allow a different partition to be specified as the home of
.android_secure using the fstab flag 'andsec'.

Using the /data/media variant of jewel as an example, recovery.fstab or
twrp.fstab could be edited like follows:

/external_sd  vfat  /dev/block/mmcblk1p1  flags=display="MicroSD";andsec

Note, this is NOT a method to move .android_secure in your ROM. Your ROM
must already write to this alternative location.

Change-Id: I3a6e4e63aaddb35870b79e80938b0f9c2c902443

gui/basicTheme/res/ui.xml

@@ -703,7 +703,10 @@
                 <placement x="%col1_x%" y="525" />
                 <font resource="font" color="white" />
                 <text>.android_secure</text>
-                <condition var1="fileexists" var2="/sdcard/.android_secure" />
+                <conditions>
+                    <condition var1="tw_has_android_secure" var2="1" />
+                    <condition var1="fileexists" var2="/and-sec" />
+                </conditions>
                 <data variable="tw_backup_andsec" />
                 <image checked="checkbox_true" unchecked="checkbox_false" />
             </object>