SMS isn't converted to MMS even after 7 segments of messages

Bug 6903793

Resurrect the mms_config.xml setting "smsToMmsTextThreshold" to allow
overlays to specify an sms->mms conversion after a certain number
of sms segments have been created. Tested on mysid, yakju, and sojus. All
three have different settings for this feature. Also tested bug fixed by

Change-Id: Ibcfd235edbaa264fede6e48f84f04345d16368fa
4 files changed