Fix errors when compiling with -Wall -Werror on Android.

This CL also turns those features on by default on Android

Review URL: https://codereview.appspot.com/7313049

git-svn-id: http://skia.googlecode.com/svn/trunk@7645 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/utils/SkRandom.h b/include/utils/SkRandom.h
index 150384d..6ab1cd1 100644
--- a/include/utils/SkRandom.h
+++ b/include/utils/SkRandom.h
@@ -197,7 +197,7 @@
      */
     float nextF() {
         unsigned int floatint = 0x3f800000 | (this->nextU() >> 9);
-        float f = *(float*)(&floatint) - 1.0f;
+        float f = *SkTCast<float*>(&floatint) - 1.0f;
         return f;
     }