Avoid an assertion failure when a bit field is extracted from a value of the same size.
Summary: One of the cases handled by ValueObjectChild::UpdateValue() uses the entire width of the parent's scalar value as the size of the child, and extracts the child by calling Scalar::ExtractBitfield(). This seems valid but APInt::trunc(), APInt::sext() and APInt::zext() assert that the bit field must not have the same size as the parent scalar. Replacing those calls with sextOrTrunc(), zextOrTrunc(), sextOrSelf() and zextOrSelf() fixes the assertion failures.
Reviewers: uweigand, labath
Subscribers: labath, lldb-commits
Differential Revision: http://reviews.llvm.org/D20355