Adding a new clang-tidy module to house CERT-specific checkers, and map...

Adding a new clang-tidy module to house CERT-specific checkers, and map existing checkers to CERT secure coding rules and recommendations for both C (https://www.securecoding.cert.org/confluence/display/c/SEI+CERT+C+Coding+Standard) and C++ (https://www.securecoding.cert.org/confluence/pages/viewpage.action?pageId=637).

llvm-svn: 249130