Updates the DW_AT_data_member_location handlers for the LLDB DWARF plugin
to handle the case of an integer constant (DWARF 3 and later).

- Fixes tests that assert in RecordLayoutBuilder::updateExternalFieldOffset
because LLDB was providing an external AST source with missing member offsets.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@187423 91177308-0d34-0410-b5e6-96231b3b80d8