[APInt] Implement APInt::intersects without creating a temporary APInt in the multiword case

Summary: This is a simple question we should be able to answer without creating a temporary to hold the AND result. We can also get an early out as soon as we find a word that intersects.

Reviewers: RKSimon, hans, spatel, davide

Reviewed By: hans, davide

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D32253

llvm-svn: 300812