[dev.power64] runtime: manually written parts for linux/power64 and linux/power64le, checkpoint

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/122430043
[dev.power64] syscall: the manually written parts for linux/power64 and linux/power64le

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/129800043
[dev.power64] syscall: auto-generated source for linux/power64 and linux/power64le.

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/127170043
[dev.power64] syscall: script changes for power64

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/123290043
[dev.power64] os/signal: support for linux/power64 and linux/power64le

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/121580043
[dev.power64] runtime: changes to the portable part for linux/power64 and linux/power64le

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/121580044
[dev.power64] runtime: move noasm_arm.goc to noasm.goc

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/121590043
[dev.power64] runtime: auto-generated headers for linux/power64 and linux/power64le

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/123280043
[dev.power64] runtime: add defs3_linux.go to generate defs_linux_power64{,le}.h

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/128070043
[dev.power64] math: implement Abs, add power64/power64le forwarding assembly functions

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/119670043
[dev.power64] sync/atomic: implement for asm_power64x.s

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/124220043
[dev.power64] cmd/9g: implement zerorange

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/121540043