added initial GLSL support to skslc

src/sksl/SkSLToken.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
  
 #ifndef SKSL_TOKEN
 #define SKSL_TOKEN
 
@@ skipping 71 matching lines @@
         CONTINUE,
         DISCARD,
         IN,
         OUT,
         INOUT,
         CONST,
         LOWP,
         MEDIUMP,
         HIGHP,
         UNIFORM,
+        FLAT,
+        NOPERSPECTIVE,
         STRUCT,
         LAYOUT,
         DIRECTIVE,
         PRECISION,
         INVALID_TOKEN
     };
 
     static std::string OperatorName(Kind kind) {
         switch (kind) {
             case Token::PLUS:         return "+";
@@ skipping 45 matching lines @@
     , fKind(kind)
     , fText(std::move(text)) {}
 
     Position fPosition;
     Kind fKind;
     std::string fText;
 };
 
 } // namespace
 #endif