[clang-tidy] Expand readability-redundant-smartptr-get to understand implicit...

[clang-tidy] Expand readability-redundant-smartptr-get to understand implicit converions to bool in more contexts.

Summary: Expand readability-redundant-smartptr-get to understand implicit converions to bool in more contexts.

Reviewers: hokein

Subscribers: klimek, xazax.hun, cfe-commits

Differential Revision: https://reviews.llvm.org/D41998

llvm-svn: 322497