Invoke initlog from forkret on first user process

Switch back to #define for PHYSTOP.  Using the E820 to retrieve the memory map is too complicated (must be done in 16-bit real-mode, probably enlarged bootblock beyond 512 bytes, and a #define requires less explanation).

Get rid of last instances of linear address and "la"
Get ready for detecting physical memory dynamically

2011

Without this, every write to the console results in log writes.

Maybe the string boot shouldn't appear in xv6 code?

usertest for big write()s
push begin_trans/commit_trans down into syscalls

Remove device mapping from bootpgdir
Remove unnecessary vmenable
Set CPUS back to 2 in Makefile
Passes all usertests

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)

Maybe not necessary, but don't want to waste time figuring this out again

All tests pass

Passes all tests now (but need to update usertests to allow for more than 640k)

Very important to give qemu memory through PHYSTOP :(