Reduce scope of MIR analysis attributes.

MIR analaysis attributes are only used in MIRGraph::AnalyzeBlock. Reduce the
scope to just the file that defines that function.
Reduce the size of the attributes from int32 to int16.
Remove the use of #defines in favor of enums.

Change-Id: I45ba3aa08beae67240507917b584d537a029838e
2 files changed