[InstCombine] Fold add nuw + uadd.with.overflow

Fold add nuw and uadd.with.overflow with constants if the
addition does not overflow.

Part of https://bugs.llvm.org/show_bug.cgi?id=38146.

Patch by Dan Robertson.

Differential Revision: https://reviews.llvm.org/D59471

llvm-svn: 356584