Deprecate DwarfUnit::addBlockByrefAddress().

The clang frontend already creates a DIExpression that replicates the
logic in addBlockByrefAddress() exactly, thus making this function
effectively unreachable. To guard against human error I'm hereby
marking the function with an assertion and let it hit the bots before
eventually removing it.

rdar://problem/31629055

llvm-svn: 315636
1 file changed