Edge antialiasing for convex shapes in Ganesh

Edge antialiasing for convex shapes in Ganesh

This patch implements edge antialiasing for convex shapes, using the fragment
shader to compare against the edge equations for each triangle.  Currently, it
only works for flat shaded primitives (i.e., it was not integrated into the
"active stages" path).  The skia.gyp changes cause this code to be compiled into
SampleApp, but do not enable the tesselated path by default.

Notes:  the SkOSWindow_Unix.cpp change is to silence a valgrind warning about
memcpy() with overlapping regions.  The GrBinHashKey change is to avoid running
a two-pass hash (GrProgramDesc is now 52 bytes or so, exceeding the 32 byte
default size).

Review URL:  http://codereview.appspot.com/4519054/

git-svn-id: http://skia.googlecode.com/svn/trunk@1314 2bbb7eff-a529-9590-31e7-b0007b416f81