Backed out part of the ABI changes that were checked in because it breaks the...

Backed out part of the ABI changes that were checked in because it breaks the i386 test suite as it makes backtraces for the first instruction of a function fail. Stepping relies on backtraces being correct, so I am reverting what is causing the breakage.

I filed this to track the fix:

<rdar://problem/12817918> Recent i386 ABI changes break the i386 test suite because stack backtracing is busted when stopped in trampolines

llvm-svn: 169409