no real big updates

just trying to change a few names
sed -i 's/gpu/lcd/g'

and changed gpu.c and header to lcd.c
actually added lcd.c and lcd.h to git database
big update to lcd and cpu

finished up most interrupts. step_gpu function is working.
still have a few loose ends with the draw sprite function and a
a lot of stuff in the draw line function to finish up. added a few
more cases for writing to io hardware registers with write_byte.
added a lot more macros including interrupts, lcd modes, periods.
also added a few timer variables to struct gb.