In thread.c, we need to cast to whatever the native
size of intptr is on the system, but we only have
uintptr available. They're the same size, but can't
do signed casts without this one :).
R=rsc
CC=golang-dev
https://golang.org/cl/156073
cgo/libmach remain unimplemented. However, compilers, runtime,
and packages are 100%. I still need to go through and implement
missing syscalls (at least make sure they're all listed), but
for all shipped functionality, this is done. Ship! ;)
R=rsc, VenkateshSrinivas
https://golang.org/cl/152142
