Change TSymbolTable::insertBuiltIn() TType* pointers to const.

Const types make it possible to implement caching and
other optimizations.

BUG=492725

Change-Id: I64398bb9effcc909dd052a038acbb5ec0ca730e8
Reviewed-on: https://chromium-review.googlesource.com/281046
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Tested-by: Dmitry Skiba <dskiba@google.com>
diff --git a/src/compiler/translator/ValidateLimitations.cpp b/src/compiler/translator/ValidateLimitations.cpp
index efb0601..f8d2306 100644
--- a/src/compiler/translator/ValidateLimitations.cpp
+++ b/src/compiler/translator/ValidateLimitations.cpp
@@ -400,7 +400,7 @@
     for (ParamIndex::const_iterator i = pIndex.begin();
          i != pIndex.end(); ++i)
     {
-        const TParameter &param = function->getParam(*i);
+        const TConstParameter &param = function->getParam(*i);
         TQualifier qual = param.type->getQualifier();
         if ((qual == EvqOut) || (qual == EvqInOut))
         {