Trying to improve x49gp

[Claudio L.]

A couple of things I noticed after applying all the patches:
* Trying to mount the SD card on newRPL showed "Unsupported CMD8 and CMD55". These are SD commands for SDHC cards. I need to double check on other computers. I could swear I implemented those on x49gp at some point.
* The menu sometimes shows up with green text (green as in the same background of the calculator screen). I think the text is being drawn as transparent?
* There were 3 errors (actually warnings) at block-vvfat.c (or vvfat-block.c, whatever) which I just silenced in the makefile (it was an Unused result value from a few functions), not sure if it's the most elegant solution.

Perhaps you would like to investigate also the ones I couldn't solve myself. In all of them, I'm using Qt Creator as IDE/debugger (but the issues happen with all debuggers in general), works great except:
* When debugging, somehow breakpoints are not set/removed properly. If the code is running, it won't pause when you insert a breakpoint (it should pause, let the debugger set the breakpoint, then continue), so you need to manually pause the code before setting any breakpoints.
* An easy one: when the debugger stops at a breakpoint, doing single step should run the instruction regardless of the presence of the breakpoint (perhaps remove it temporarily, execute, then re-apply the breakpoint). Right now it won't single-step, you need to manually disable the breakpoint or it will be triggered every time.
* When single-stepping through the code, there has to be a way to avoid stepping through IRQs. Right now as soon as an IRQ is triggered, you start single-stepping through its code, making it impossible to debug the main application.