[Clang-tidy] check for malloc, realloc and free calls

Summary:
This checker flags the use of C-style memory management functionality and notes about modern alternatives.
In an earlier revision it tried to autofix some kind of patterns, but that was a bad idea. Since memory management can be so widespread in a program, manual updating is most likely necessary.
Maybe for special cases, there could be later additions to this basic checker.

This is the first checker I wrote and I never did something with clang (only compiling programs). So whenever I missed conventions or did plain retarded stuff, feel free to point it out! I am willing to fix them and write a better checker.

I hope the patch does work, I never did this either. On a testapply in my repository it did, but I am pretty unconfident in my patching skills :)

Reviewers: aaron.ballman, hokein, alexfh, malcolm.parsons

Subscribers: cfe-commits, JDevlieghere, nemanjai, Eugene.Zelenko, Prazek, mgorny, modocache

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D26167

Patch by Jonas Toth!

llvm-svn: 289546