Invoke initlog from forkret on first user process

Allocate proper kernel page table immediately in main using boot allocator
Remove pginit
Simplify address space layout a tiny bit
More to come (e.g., superpages to simplify static table)

Very important to give qemu memory through PHYSTOP :(

Variable declarations at top of function,
separate from initialization.

Use == 0 instead of ! for checking pointers.

Consistent spacing around {, *, casts.

Declare 0-parameter functions as (void) not ().

Integer valued functions return -1 on failure, 0 on success.

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

Simplify allocuvm/deallocuvm to operate in a contiguous memory model.  This makes their interface match up better with proc->sz and also simplifies the callers (it even gets the main body of exec on one page).

Rearrange proc.h and proc.c to get our action-packed spreads back (mostly).  They also make sense in this order, so it's not just for page layout.

do not keep sorted contiguous free list

put an invalid page below the stack
have fork() handle invalid pages

fix corner cases with alignment when mapping kernel ELF file

Includes code for TLB shootdown (which actually seems unnecessary for xv6)

this time do it ourselves instead of piggybacking on TLS.
add -fno-pic to Makefile; pic code breaks our fake TLS.

still not quite but a lot better.

 * rename c/cp to cpu/proc
 * rename cpu.context to cpu.scheduler
 * fix some comments
 * formatting for printout

pdf has very good page breaks now.
would be a good copy for fall 2009.

group locks into structs they protect.
few naming nits.

Some proc cleanup, moving some of copyproc into allocproc.

Also, an experiment: use "thread-local" storage for c and cp
instead of the #define macro for curproc[cpu()].

timer-preempted kernel thread resumes execution in trap() after yield().
otherwise the kernel could get an arbitrary number of nested timer intrs.