Add an error to check that all program scope variables are in the constant address space in OpenCL.
<rdar://problem/13477795>

crashlog.py was always subtracting 1 to point to the previous instruction when symbolicating ARM backtraces. Many times the backtraces will include bit zero set to 1 to indicate thumb, so we need to make sure we mask the address and then backup one for non frame zero frames.