[clang-tidy] Add check 'readability-redundant-member-init'

Summary: The check emits a warning if a member-initializer calls the member's default constructor with no arguments.

Reviewers: sbenza, alexfh, aaron.ballman

Subscribers: modocache, mgorny, Eugene.Zelenko, etienneb, Prazek, hokein, cfe-commits, beanz

Differential Revision: https://reviews.llvm.org/D24339

llvm-svn: 284742