Add skip to field packer.

remove hsb functions from env headers.
add RS_PACKED define for packed structures.

Change-Id: Idc661edff85c0047baa201f43e0839ac82c74593

graphics/java/android/renderscript/FieldPacker.java

@@ -40,6 +40,10 @@ public class FieldPacker {
         mPos = i;
     }
 
+    public void skip(int i) {
+        mPos += i;
+    }
+
     public void addI8(byte v) {
         mData[mPos++] = v;
     }