On Darwin and FreeBSD, the mmap syscall return value is returned
unmodified. This means that the return value will either be a
valid address or a positive error number.
Also check return value from mmap in SysReserve - the callers of
SysReserve expect nil to be returned if the allocation failed.
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/7871043
Collapse the arch,os-specific directories into the main directory
by renaming xxx/foo.c to foo_xxx.c, and so on.
There are no substantial edits here, except to the Makefile.
The assumption is that the Go tool will #define GOOS_darwin
and GOARCH_amd64 and will make any file named something
like signals_darwin.h available as signals_GOOS.h during the
build. This replaces what used to be done with -I$(GOOS).
There is still work to be done to make runtime build with
standard tools, but this is a big step. After this we will have
to write a script to generate all the generated files so they
can be checked in (instead of generated during the build).
R=r, iant, r, lucio.dere
CC=golang-dev
https://golang.org/cl/5490053
