Alias Analysis Improvement patch

[law@redhat.com]

In message <3EE956B1.8000008@noida.hcltech.com>, "Sanjiv Kumar Gupta, Noida" wr
ites:
 >That would be source level information carried down to the RTL, but
 >IMHO that may not cope with the address arithmetic involving temporaries.
It should cope with address arithmetic just fine once we have either
PTA enabled by default or do something like base address analysis.

In fact, it ought to do quite a bit better than the tracking through
arithmetic we currently try to do in alias.c.

Jeff