Patch to change ARM register name set

[Richard Earnshaw]

A couple of niggles rather than anything consequential.

Despite what I said about APCS reg names, the usage of r13, r14 and r15 is 
so tightly defined by the architecture that I think it is worth preserving 
the apcs-style names (sp, lr & pc respectively) for these even if using 
the standard names.  Use of 'fp' for r11 is more debatable since this 
really is an apcs option.

Second, the option to select this is, I think, a little unobvious unless 
you already know what it is all about (what does "-M standard-names" 
mean?).  I'd prefer the option to be
	--disassembler-options=reg-names-std
or
	--disassembler-options=reg-names-apcs

That way it is clear that the option refers to the register names and not 
to some other feature of disassembly.

Maybe there should be a
	--disassembler-options=reg-names-raw
as well, that only uses r0-r15 as the names.