swift234

Do emit diagnostics on UnreachableInst that result from mandatory inlining.

If these are actually resulting from something we should diagnose, we
should have already emitted diagnostics on these when emitting
diagnostics on the callee function.

This was reported as a compiler crash resulting from hitting an
llvm_unreachable() in the diagnostics code because we're attempting to
emit a diagnostic about a constructor not having a return value on some
path (and the code does not expect to be emitting these diagnostics from
constructors).

It turns out this was extremely difficult to reproduce because it
required a constructor with a compiler generated apply to a function
with an UnreachableInst in it that does not get replaced by another
diagnostics pass, DiagnoseUnreachable.

To satisfy the last of these conditions, I've added '-assert-config
Release' to the run line, because this results in a call to a no-return
function (one of the fatal error reporting functions) not getting
emitted because it is stripped out due to the assert configuration (and
DiagnoseUnreachable would have stripped the code after the no-return
function, and that code would have included the UnreachableInst that
triggers the crash this is fixing).

Fixes the rest of rdar://problem/20663080.

Swift SVN r28452