Having the compiler count the number of array elements speeds up Gamma from 63.7 to 56.6 ns/op.
R=rsc, golang-dev, r
CC=golang-dev
https://golang.org/cl/5362043
The letter is a holdover from C and unnecessary in Go.
Gofix module included.
Fixes#2306.
R=golang-dev, gri, dsymonds
CC=golang-dev
https://golang.org/cl/5158043