Quick compiler: fix array overrun.

MIRGraph::InlineCalls() was using the MIR opcode to recover
Dalvik instruction flags - something that is only valid for
Dalvik opcodes and not the set of extended MIR opcodes.

This is probably the 3rd or 4th time we've had a bug using
the MIR opcode in situations that are only valid for the Dalvik
opcode subset.  I took the opportunity to scan the code for
other cases of this (didn't find any), and did some cleanup while
I was in the neighborhood.

We should probably rework the DalvikOpcode/MirOpcode model whenver we
get around to removing DalvikInstruction from MIR.

Internal bug b/15352667: out-of-bound access in mir_optimization.cc

Change-Id: I75f06780468880892151e3cdd313e14bfbbaa489