HLSL: Add string basic type and recognize string declaration grammar.

This includes the "< decl ; decl ; >" syntax which has its own namespace.
This functionality is not implemented, just silently accepted.

glslang/Include/BaseTypes.h

@@ -55,6 +55,10 @@ enum TBasicType {
     EbtSampler,
     EbtStruct,
     EbtBlock,
+
+    // HLSL types that live only temporarily.
+    EbtString,
+
     EbtNumTypes
 };
 

glslang/Include/revision.h

@@ -2,5 +2,5 @@
 // For the version, it uses the latest git tag followed by the number of commits.
 // For the date, it uses the current date (when then script is run).
 
-#define GLSLANG_REVISION "Overload400-PrecQual.1499"
+#define GLSLANG_REVISION "Overload400-PrecQual.1501"
 #define GLSLANG_DATE "19-Sep-2016"