Track whether function declarations are prototypes, and only allow at most one prototype for ES 100.

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@24342 e7fa87d3-cd2b-0410-9028-fcbf551c1848

Test/300.vert

@@ -147,3 +147,13 @@ int[] foo213234();        // ERROR
 int foo234234(float[]);   // ERROR
 int foo234235(vec2[] v);  // ERROR
 precision highp float[2]; // ERROR
+
+int fffg(float f);
+int fffg(float f);
+
+int gggf(float f);
+int gggf(float f) { return 2; }
+int gggf(float f);
+
+int agggf(float f) { return 2; }
+int agggf(float f);