Improve C++ function name handling and step-in avoid regerxp handling

If the function is a template then the return type is part of the
function name. This CL fixes the parsing of these function names in
the case when the return type contains ':'.

The name of free functions in C++ don't have context part. Fix the
logic geting the function name without arguments out from a full
function name to handle this case.

Change the handling of step-in-avoid-regexp to match the value against
the function name without it's arguments and return value. This is
required because the default regex ("^std::") would match any template
function returning an std object.

Fifferential revision: http://reviews.llvm.org/D11461

llvm-svn: 243099