Update documentation.

- Convert http to https, provide archive link when possible.
- Made CPU-JIT.png more readable on dark themes;
Added a white background so there isn't black text on a black
background.

src/xenia/cpu/ppc/ppc_emit_fpu.cc

@@ -26,7 +26,7 @@ using xe::cpu::hir::RoundMode;
 using xe::cpu::hir::Value;
 
 // Good source of information:
-// http://mamedev.org/source/src/emu/cpu/powerpc/ppc_ops.c
+// https://github.com/mamedev/historic-mame/blob/master/src/emu/cpu/powerpc/ppc_ops.c
 // The correctness of that code is not reflected here yet -_-
 
 // Enable rounding numbers to single precision as required.