Fix a few cases where enum constant handling was using

Fix a few cases where enum constant handling was using
ASTContext::getTypeSize() rather than ASTContext::getIntWidth() for
the width of an integral type. The former includes padding for bools
(to the target's size) while the latter does not, so we woud end up
zero-extending bools to the target width when we shouldn't. Fixes a
crash-on-valid in the included test.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@101372 91177308-0d34-0410-b5e6-96231b3b80d8