Implement support for fast isel of calls of i1 arguments, even though they are illegal,

Implement support for fast isel of calls of i1 arguments, even though they are illegal,
when they are a truncate from something else.  This eliminates fully half of all the
fastisel rejections on a test c++ file I'm working with, which should make a substantial
improvement for -O0 compile of c++ code.

This fixed rdar://9297003 - fast isel bails out on all functions taking bools

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129752 91177308-0d34-0410-b5e6-96231b3b80d8