First life-signs of type functions

[Stefan Koch]

Hello Guys,

After a bit of fiddling the following code (and only that because 
I need do partial evaluation of the semantic pass on the function 
body manually ...)
Now works on the Talias branch

string F(alias y)
{
     return y.stringof;
}
static assert(F!(ulong) == "ulong");
static assert(F!(uint) == "uint");