Implement copyout.9 and a draft of pmap_load with various fixes

Fix toolchain to not add underscores to C symbols when calling them from assembly
(define the builtin NO_LEADING_UNDERSCORE)

Fix intr.h, put _splraise() definition in intr.c

Add empty files for uart and timer SoC peripherals

Add information about files containing copyin/copyout/etc implementations for other archs in TODO file

Add a few defines in genassym.cf