Add ES 300 built-ins trunc, round, roundEven, modf, isnan, isinf, floatBitsToInt, floatBitsToUint, intBitsToFloat, uintBitsToFloat, packSnorm2x16, unpackSnorm2x16, packUnorm2x16, unpackUnorm2x16, packHalf2x16, and unpackHalf2x16, and new form of min, max, clamp, and mix.

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@21063 e7fa87d3-cd2b-0410-9028-fcbf551c1848

Test/precision.frag

@@ -30,6 +30,11 @@ void main()
     precision lowp int;
     int level1_low;
     sum += level1_low;
+    
+    // test maxing precisions of args to get precision of builtin
+    lowp float arg1;
+    mediump float arg2;
+    lowp float d = distance(arg1, arg2);
 
     {
         int level2_low;