Invariant keyword support

Added support for the invariant keyword in the parser.
Also made sure all in/out types were handled properly
in OutputASM.cpp.

Change-Id: I40f0bc9caf5bccc691aa60dfaa90bed5d1d7d238
Reviewed-on: https://swiftshader-review.googlesource.com/3663
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>

src/OpenGL/compiler/ParseHelper.cpp

diff --git a/src/OpenGL/compiler/ParseHelper.cpp b/src/OpenGL/compiler/ParseHelper.cpp
index f27486e..2fa4512 100644
--- a/src/OpenGL/compiler/ParseHelper.cpp
+++ b/src/OpenGL/compiler/ParseHelper.cpp
@@ -1053,6 +1053,24 @@
 	return false;
 }
 
+void TParseContext::es3InvariantErrorCheck(const TQualifier qualifier, const TSourceLoc &invariantLocation)
+{
+	switch(qualifier)
+	{
+	case EvqVaryingOut:
+	case EvqSmoothOut:
+	case EvqFlatOut:
+	case EvqCentroidOut:
+	case EvqVertexOut:
+	case EvqFragmentOut:
+		break;
+	default:
+		error(invariantLocation, "Only out variables can be invariant.", "invariant");
+		recover();
+		break;
+	}
+}
+
 bool TParseContext::supportsExtension(const char* extension)
 {
     const TExtensionBehavior& extbehavior = extensionBehavior();