Update assumption in template diffing about integer template arguments.

Update assumption in template diffing about integer template arguments.

Fix for PR22017.  Integer template arguments are automatically bit extended to
the size of the integer type.  In template diffing, evaluated expressions were
not having their results extending, leading to comparing two APSInt's with
different widths.  Apply the proper bit extending when evaluating template
arguments.  This mainly affected bool template arguments.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@230603 91177308-0d34-0410-b5e6-96231b3b80d8