[dmd-internals] eliminating __DBLULNG, etc.

[Walter Bright]

In case anyone was wondering, I've been moving this code into the code 
generator. I've already done it for the trace.d assembler code, and some of the 
llmath.d code. I've been moving more in because it makes it easier to retarget 
D. Every ABI difference causes me to have to carefully go through that stuff 
again. And none of that code is useful for gdc or ldc.

Having the code generator inline it also makes for faster code.

After another release cycle, those should all be removed from trace.d and 
llmath.d. Leaving them in until then makes doing things like git bisect easier.