Generate nuw GEPs for struct member accesses, as inbounds + non-negative
implies nuw.
Regression tests are updated using update scripts where possible, and by
find + replace where not.
The previous assertion was relatively easy to trigger, and likely will
be easy to trigger going forward. EmitDelegateCallArg is relatively
popular.
This cleanly diagnoses PR28299 while I work on a proper solution.
llvm-svn: 348991
