delete most comments from bootother.S (since copy of bootasm.S)
ksegment() -> seginit()
move more stuff from main() to mainc()

find out the hard way why user and kernel must have separate segment descriptors

do Bochs breakpoint and spin in bootasm.S.
not needed in bootmain too.
fix readseg bug (rounding of va).
zero segments when memsz > filesz.
no need to clear BSS in kernel main.
make bootother.S like bootasm.S

Rework comments a bit.

Move initialization of %sp after
protected mode jump and change to %esp.

don't use the same name for two different pieces of code

and plan 9 code, at least boots and gets into C code.