A template to emit ARM asm

[dwhall256]

Good suggestion, Peter. It makes sense. I tried turning `AHB1ENR` to an inline 
proc. It resolved the error, but the procedure was called a second time after 
the `asm` statement, overwriting the modification to the variable. So a tried 
turning more of the templates into inline procs. I got something that appears 
to work at the C level. Next, I need to inspect the assembly to be sure the C 
funcs are truly inlined; otherwise, I'll keep trying various combinations of 
templates.