text/template: allow comparison functions to work between any integers
Previously, signed and unsigned integers could not be compared, but
this has problems with things like comparing 'x' with a byte in a string.
Since signed and unsigned integers have a well-defined ordering,
even though their types are different, and since we already allow
comparison regardless of the size of the integers, why not allow it
regardless of the sign?

Integers only, a fine place to draw the line.

Fixes issue 7489.

LGTM=adg
R=golang-codereviews, adg
CC=golang-codereviews
https://codereview.appspot.com/149780043
fmt: make printing of ints 25-35% faster
Inspired by a remark by Leonard Holz, use constants for division

BenchmarkSprintfEmpty           130           132           +1.54%
BenchmarkSprintfString          438           437           -0.23%
BenchmarkSprintfInt             417           414           -0.72%
BenchmarkSprintfIntInt          663           691           +4.22%
BenchmarkSprintfPrefixedInt     791           774           -2.15%
BenchmarkSprintfFloat           701           686           -2.14%
BenchmarkManyArgs               2584          2469          -4.45%
BenchmarkFprintInt              488           357           -26.84%
BenchmarkFprintIntNoAlloc       402           265           -34.08%
BenchmarkScanInts               1244346       1267574       +1.87%
BenchmarkScanRecursiveInt       1748741       1724138       -1.41%

Update issue 3463

LGTM=josharian, rsc
R=golang-codereviews, josharian, rsc
CC=golang-codereviews
https://codereview.appspot.com/144250043