Add support for EXT_YUV_target

Add new sampler type "__samplerExternal2DY2YEXT"
to sample a YUV texture image and output color value
without any color conversion,
new additional type to specify color space standard formula and
built-in functions for yuv to rgb transformation.

Change-Id: I1780650fe84cd75191c1ca1e4118e89d585bfd92
Reviewed-on: https://chromium-review.googlesource.com/454697
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/compiler/translator/intermOut.cpp b/src/compiler/translator/intermOut.cpp
index 6312ef7..af2c199 100644
--- a/src/compiler/translator/intermOut.cpp
+++ b/src/compiler/translator/intermOut.cpp
@@ -609,9 +609,14 @@
                 out << node->getUnionArrayPointer()[i].getUConst();
                 out << " (const uint)\n";
                 break;
+            case EbtYuvCscStandardEXT:
+                out << getYuvCscStandardEXTString(
+                    node->getUnionArrayPointer()[i].getYuvCscStandardEXTConst());
+                out << " (const yuvCscStandardEXT)\n";
+                break;
             default:
                 out.prefix(SH_ERROR);
-                out << "Unknown constant";
+                out << "Unknown constant\n";
                 break;
         }
     }