[clang-tidy] add checks to bugprone-posix-return

This check now also checks if any calls to pthread_* functions expect negative return values. These functions return either 0 on success or an errno on failure, which is positive only.

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@372037 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed