Returns R14 and R15 to the available register pool.
Plays more nicely with ELF ABI C code.
In particular, our signal handlers will no longer crash
when a signal arrives during execution of a cgo C call.
Fixes#720.
R=ken2, r
CC=golang-dev
https://golang.org/cl/1847051
add "extern register" support to 8c.
extern register means allocate in the FS-relative segment.
make 8l generate segmented stack checks.
R=ken
OCL=26600
CL=26606
these guys really really want long to be 32-bits,
so ,s/long/int32/ (and then manual fixup).
still passes all tests.
(i started out looking for just those longs that
needed to be int32 instead, and it was just too hard
to track them down one by one.)
the longs were rare enough that i don't think
it will cause integration problems.
R=ken
OCL=13787
CL=13789
