Parser: Implement extension GL_AMD_gpu_shader_half_float.

- Add built-in types: float16_t, f16vec, f16mat.
- Add support of half float constant: hf, HF.
- Extend built-in floating-point operators: +, -, *, /, ++, --, +=, -=,
  *=, /=, ==, !=, >=, <=, >, <.
- Add support of type conversions: float16_t -> XXX, XXX -> float16_t.
- Add new built-in functions.

glslang/MachineIndependent/SymbolTable.cpp

@@ -60,6 +60,9 @@ void TType::buildMangledName(TString& mangledName)
     switch (basicType) {
     case EbtFloat:              mangledName += 'f';      break;
     case EbtDouble:             mangledName += 'd';      break;
+#ifdef AMD_EXTENSIONS
+    case EbtFloat16:            mangledName += "f16";    break;
+#endif
     case EbtInt:                mangledName += 'i';      break;
     case EbtUint:               mangledName += 'u';      break;
     case EbtInt64:              mangledName += "i64";    break;