fix issues 10277 & 6045:improve demangling for function local symbols

http://d.puremagic.com/issues/show_bug.cgi?id=6045
http://d.puremagic.com/issues/show_bug.cgi?id=10027

allows function names as part of a qualified name, removing return type and function attributes. The compiler does this as well with \__PRETTY_FUNCTION__, but also removes function arguments which probably is too much.

This needs https://github.com/D-Programming-Language/phobos/pull/1592 to pass unittests.