internal/syscall: add support for getrandom on arm

Added in linux commit eb6452537b28

LGTM=agl
R=agl
CC=golang-codereviews
https://codereview.appspot.com/130170043
runtime: add more cases to GC info test

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews, khr, rlh, rsc
https://codereview.appspot.com/125420043
unicode: strconv: regexp: Upgrade to Unicode 7.0.0.

LGTM=r, bradfitz
R=r, bradfitz
CC=golang-codereviews
https://codereview.appspot.com/127470043