Rect types.
The actual image representation is unchanged. A future change will
replace the {[][]color} with {[]color, stride int, r Rectangle} and
possibly a clip region.
The draw.Color, draw.Point and draw.Rect types will be removed in a
future change. Trying to do it in this one polluted the diff with
trivia.
R=r, rsc
CC=golang-dev
https://golang.org/cl/1918047
the bash scripts and makefiles for building go didn't take into account
the fact $GOROOT / $GOBIN could both be directories containing whitespaces,
and was not possible to build it in such a situation.
this commit adjusts the various makefiles/scripts to make it aware of that
possibility, and now it builds successfully when using a path with whitespaces
as well.
Fixes#115.
R=rsc, dsymonds1
https://golang.org/cl/157067
