telephony: Add support for additional emergency numbers

 * Some devices intended for international sale do not return proper
   emergency numbers in the ril.ecclist property.
 * Add support for a static list of emergency numbers to be appended
   to the list supplied by the radio.
 * Set "ro.ril.ext.ecclist" to use this.

http://review.cyanogenmod.org/#/c/54194/

Change-Id: I7a6cedadf6f7c0b576e6f08a0660b5e4c34af61b