Feature: __FUNCTION__ to give name of parent function.

[Iain Buclaw]

This was a question asked in IRC, someone wanting a way to have the parent function
name outputted for logging purposes. Just like there is __LINE__ and __FILE__ for
access to the line number and filename, would be handy (and trivial to implement)
if there was a __FUNCTION__ variable also for outputting the bare name of the
function. Optionally could also add a __PRETTY_FUNCTION__ too for outputting the
type signature of the function.

ie:
writeln(__FUNCTION__); // foo
writeln(__PRETTY_FUNCTION__); // int foo(string)

Regards