drd: Add a consistency check

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14790 a5019735-40e9-0310-863c-91ae7b9d1cf9
Bug 341238. Recognize GCC5/DWARFv5 DW_LANG constants Go, C11, C++11, C++14.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14791 a5019735-40e9-0310-863c-91ae7b9d1cf9