[LLDB] Fix Clang-tidy misc-use-override warnings in some files in...

 [LLDB] Fix Clang-tidy misc-use-override warnings in some files in include/lldb/Core; other minor fixes.

Summary:
This is second attempt based on current code.

I checked this patch on my own build on RHEL 6.

Please check it in if it's OK, because I don't have SVN write access.

Patch by Eugene Zelenko.

Reviewers: labath, brucem, clayborg

Subscribers: amccarth, lldb-commits

Differential Revision: http://reviews.llvm.org/D13574

llvm-svn: 249928