Clean up physical coupling

Narrow the use of #include directives in hwui, replacing with forward
declarations where straightforward. Speeds compiles; doesn't do any
restructuring of code.

Change-Id: Icac2baffb5896f55d8c6718e9bd9d4bfa02d3ca0
diff --git a/libs/hwui/Dither.h b/libs/hwui/Dither.h
index 546236be..092ebf2 100644
--- a/libs/hwui/Dither.h
+++ b/libs/hwui/Dither.h
@@ -19,12 +19,11 @@
 
 #include <GLES3/gl3.h>
 
-#include "Program.h"
-
 namespace android {
 namespace uirenderer {
 
 class Caches;
+class Program;
 
 // Must be a power of two
 #define DITHER_KERNEL_SIZE 4