Move SkBitSet to utils.

Review URL: https://codereview.appspot.com/5875043

git-svn-id: http://skia.googlecode.com/svn/trunk@3460 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gyp/utils.gyp b/gyp/utils.gyp
index 1847e95..e30b433 100644
--- a/gyp/utils.gyp
+++ b/gyp/utils.gyp
@@ -37,6 +37,8 @@
 
         '../src/utils/SkBase64.cpp',
         '../src/utils/SkBase64.h',
+        '../src/utils/SkBitSet.cpp',
+        '../src/utils/SkBitSet.h',
         '../src/utils/SkBoundaryPatch.cpp',
         '../src/utils/SkCamera.cpp',
         '../src/utils/SkColorMatrix.cpp',