Fold user-definedness of function nodes into TOperator

Whether a function call is user-defined is not orthogonal to TOperator
associated with the call node - other ops than function calls can't be
user-defined. Because of this it makes sense to store the user-
definedness by having different TOperator enums for different types of
calls.

This patch also tags internal helper functions that have a raw
definition outside the AST with a separate TOperator enum. This way
they can be handled with logic that is easy to understand. Before this,
function calls like this left the user-defined bit unset, despite not
really being built-ins either. The EmulatePrecision traverser uses
this. This is also something that could be used to clean up built-in
emulation in the future.

BUG=angleproject:1490
TEST=angle_unittests

Change-Id: I597fcd9789d0cc22b689ef3ce5a0cc3f621d4859
Reviewed-on: https://chromium-review.googlesource.com/433443
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
diff --git a/src/compiler/translator/SymbolTable.cpp b/src/compiler/translator/SymbolTable.cpp
index c9ccd2b..3ba0223 100644
--- a/src/compiler/translator/SymbolTable.cpp
+++ b/src/compiler/translator/SymbolTable.cpp
@@ -158,7 +158,7 @@
 TFunction *TSymbolTable::findBuiltInOp(TIntermAggregate *callNode, int shaderVersion) const
 {
     ASSERT(!callNode->isConstructor());
-    ASSERT(callNode->getOp() != EOpFunctionCall);
+    ASSERT(!callNode->isFunctionCall());
     TString opString = GetOperatorString(callNode->getOp());
     // The return type doesn't affect the mangled name of the function, which is used to look it up.
     TType dummyReturnType;