Strip debug info when inlining into a nodebug function.

The LLVM backend cannot produce any debug info for an llvm::Function
without a DISubprogram attachment. When inlining a debug-info-carrying
function into a nodebug function, there is therefore no reason to keep
any debug info intrinsic calls or debug locations on the instructions.

This fixes a problem discovered in PR32042.

rdar://problem/30679307

llvm-svn: 296488