add SDL support



git-svn-id: http://skia.googlecode.com/svn/trunk@182 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/samplecode/SamplePathEffects.cpp b/samplecode/SamplePathEffects.cpp
index 4e964d7..e2b5f5a 100644
--- a/samplecode/SamplePathEffects.cpp
+++ b/samplecode/SamplePathEffects.cpp
@@ -203,7 +203,7 @@
         }
         
         gPhase -= SK_Scalar1;
-        this->inval(nil);
+        this->inval(NULL);
         
         SkPaint paint;