Temporarily relax a check in the debug info verifier.

The clang frontend helps out GDB by emitting the members of local anonymous
unions as artificial local variables with shared storage. When SROA splits
the storage for artificial local variables that are smaller than the entire
union, the overhang piece will be outside of the allotted space for the
variable and this check fails.

rdar://problem/20730771

llvm-svn: 236124