hide the Hinter implementation in the freetype/truetype package.

LGTM=bsiegert
R=bsiegert
CC=golang-codereviews
https://codereview.appspot.com/58940043

testdata/, in anticipation of having other test data.

R=dsymonds
CC=bsiegert, golang-dev
https://codereview.appspot.com/14361044

to package truetype.

R=bsiegert
CC=golang-dev
http://codereview.appspot.com/6427062

Also update freetype/truetype for s/int/rune/.

R=rsc, bradfitz
CC=golang-dev
http://codereview.appspot.com/5505067

R=r, nigeltao_gnome, adg
CC=golang-dev
http://codereview.appspot.com/2527041

just version 2. The FTL (Freetype Licence) is still available. This
matches the original Freetype library (written in C).

This only expands and does not further restrict the licensing options
available to users of the freetype-go library.

R=adg
CC=golang-dev
http://codereview.appspot.com/1731049

draw text onto an image.

This is a simple API that doesn't handle line breaking, ligatures,
right-to-left or vertical scripts, and other fancy features.

R=r, rsc
CC=golang-dev
http://codereview.appspot.com/1121045

Parsing a malformed TTF may result in an index out-of-bounds panic,
rather than guaranteeing to return an error. This may be tightened
in the future.

R=r, rsc
CC=golang-dev
http://codereview.appspot.com/940044