* rename PORT.sh -> mkall.sh (hopefully more obvious),
change behavior: run commands by default.
* pull more constants out of #defines automatically,
instead of editing large lists by hand.
* add Recvfrom, Sendto
add os.O_EXCL.
R=r
http://go/go-review/1017009
* use 64-bit file system calls (Linux, Darwin)
* use 32-bit [sic] uid/gid calls (Linux)
* fix sockets on Linux
Darwin/386 works again.
Linux/386 is better but must never have worked;
there are still bugs surrounding the creation of new
threads in the runtime package.
R=austin
DELTA=1332 (673 added, 614 deleted, 45 changed)
OCL=30327
CL=30380
