[clang-tidy] Ignore ExprWithCleanups when looking for else-after-throw

Summary:
The readability-else-after-return check was not warning about
an else after a throw of an exception that had arguments that needed
to be cleaned up.

Reviewers: aaron.ballman, alexfh, djasper

Reviewed By: aaron.ballman

Subscribers: lebedev.ri, klimek, xazax.hun, cfe-commits

Differential Revision: https://reviews.llvm.org/D40505

llvm-svn: 319174