Added rename-operator pass that converts operator functions (e.g. operator +) to regular functions

[strimo378]

A pass to rename operator functions (e.g. operator +) to regular function names op1, op2, ... Relevant operators are replaced by function calls, e.g. a + b => a.op1(b). The pass renames all functions with --count=1 and single functions with >= 2.

[marxin]

Thanks for that!