Add helpers for checking if a value is a target boolean constant.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205335 91177308-0d34-0410-b5e6-96231b3b80d8
Make isSetCCEquivalent respect the TargetBooleanContents

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205336 91177308-0d34-0410-b5e6-96231b3b80d8
isTargetWindows() renamed to isTargetKnownWindowsMSVC()
to reflect its current functionality.

Based on Takumi NAKAMURA suggestion.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205338 91177308-0d34-0410-b5e6-96231b3b80d8