Enable 64-bit builds on Windows

Encountered compile errors passing 64-bit size_t to
SkIntToScalar and needed to make adjustments to
gm/gradients.cpp and bench/PicturePlaybackBench.cpp.

Verified on my local Linux, Mac, and Windows machines.

As of this change, the skia_arch_width gyp define
actually forces a 32/64-bit build on Linux, Mac, and
Windows.
Review URL: https://codereview.appspot.com/6460112

git-svn-id: http://skia.googlecode.com/svn/trunk@5195 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/bench/PicturePlaybackBench.cpp b/bench/PicturePlaybackBench.cpp
index ebb5424..7cdbccf 100644
--- a/bench/PicturePlaybackBench.cpp
+++ b/bench/PicturePlaybackBench.cpp
@@ -119,7 +119,7 @@
                     if (fDrawPosH)
                         pos[i].set(x + advX, y);
                     else
-                        pos[i].set(x + advX, y + SkIntToScalar(i));
+                        pos[i].set(x + advX, y + i);
                     advX += adv[i];
                 }