Exposing an existing checker under the name cert-err61-cpp, as it corresponds...

Exposing an existing checker under the name cert-err61-cpp, as it corresponds to the CERT C++ secure coding rule: https://www.securecoding.cert.org/confluence/display/cplusplus/ERR61-CPP.+Catch+exceptions+by+lvalue+reference

llvm-svn: 250221