Com_DPrintf as a variadic macro!

Com_DPrintf is a variadic macro now, is the equivalent of
a more detailed Com_DPrintfEx function which takes all the
C99 goodies and formats them into a rich and detailed message.

Thanks to C99 cool stuff, Com_DPrintf can show more detailed information
like __FILE__ and __LINE__ relative info (this is C89 but through
variadic macros they are very useful) and the new guy __func__