[ms] Do lookup in dependent base classes also when overload resolution fails (PR23810)

This patch does two things in order to enable compilation of the problematic code in PR23810:

1. In Sema::buildOverloadedCallSet, it postpones lookup for MS mode when no
viable candidate is found in the overload set. Previously, lookup would only
be postponed here if the overload set was empty.

2. Make BuildRecoveryCallExpr call Sema::DiagnoseEmptyLookup under more circumstances.
There is a comment in DiagnoseTwoPhaseLookup that says "Don't diagnose names we find in
classes; we get much better diagnostics for these from DiagnoseEmptyLookup." The problem
was that DiagnoseEmptyLookup might not get called later, and we failed to recover.

Differential Revision: http://reviews.llvm.org/D10369

llvm-svn: 239558