W3C Telephony API implementation.

Implements the latest W3C Telephony API specification found at http://telephony.sysapps.org/
Requires the oFono telephony middleware and the BlueZ Bluetooth middleware for working with paired phones.

BUG=XWALK-1419
Interesting, I tried assigning string with a char* but not seeing any error. gchar* shouldn't causing error as well...
If you still see compiler error then just keep it.