i#1551 port to ARM: Thumb writes to PC do not change mode
i#1551 port to ARM: Thumb writes to PC do not change mode

Updates indirect branch handling to set the LSB to 1 for a write to the PC in
Thumb mode, as such a branch does *not* change modes.

Review-URL: https://codereview.appspot.com/206740043

bl4ckic3/dynamorio,daksunt/dynamorio,AmesianX/dynamorio,code4bones/dynamorio,daksunt/dynamorio,sigma-random/dynamorio,sigma-random/dynamorio,sigma-random/dynamorio,daksunt/dynamorio,sigma-random/dynamorio,code4bones/dynamorio,AmesianX/dynamorio,bl4ckic3/dynamorio,AmesianX/dynamorio,code4bones/dynamorio,sigma-random/dynamorio,daksunt/dynamorio,bl4ckic3/dynamorio,code4bones/dynamorio,daksunt/dynamorio,bl4ckic3/dynamorio,AmesianX/dynamorio,bl4ckic3/dynamorio,AmesianX/dynamorio,code4bones/dynamorio