Add some uncovered attribute tests

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186538 91177308-0d34-0410-b5e6-96231b3b80d8
Handle '.' correctly in hex float literal parsing.

There were a couple of different loops that were not handling
'.' correctly in APFloat::convertFromHexadecimalString; these mistakes
could lead to assertion failures and incorrect rounding for overlong
hex float literals.

Fixes PR16643.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186539 91177308-0d34-0410-b5e6-96231b3b80d8
Fix a comment.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186541 91177308-0d34-0410-b5e6-96231b3b80d8
Add an explicit operator bool conversion to DIDescriptor to make
it clear what we want to do. Unfortunately the conversion to
pointer operator fires now instead and chasing down all of the
conversions and making them explicit and handled is a large task
so add a FIXME with it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186543 91177308-0d34-0410-b5e6-96231b3b80d8