LiquidSmooth/android_system_vold — pull request #1 by iiD4x (2014-04-16 14:20:53+00:00)
Title: needed for STE to avoid low data partition

vold: allow pre-configured device pairs to switch mountpoints
By setting persistent system properties
persist.sys.vold.switchexternal=1
persist.sys.vold.switchablepair=sdcard0,sdcard1 (for example)
two non-emulated extended storage devices can swap between primary
and secondary storage.

This commit is heavily inspired by Rick Fernie and Ricardo Cerqueira's
"vold: Allow pre-configured device pairs to switch mountpoints"
[http://review.cyanogenmod.org/12764] but adapted to CM's newer vold.

Change-Id: I2be5d4799c2d8f04a535096ac4c7619849f1f84a