Array of Array prep: Turn a batch of 0's into nullptr or UnsizedArraySize.

Added some const as well. This will remove camouflage of the next commit,
which will add the bulk of Array of Array semantics and functionality.
(Note the basic grammar and data structure is already in place.)

glslang/MachineIndependent/limits.cpp

@@ -133,7 +133,7 @@ void TParseContext::inductiveLoopBodyCheck(TIntermNode* body, int loopId, TSymbo
 {
     TInductiveTraverser it(loopId, symbolTable);
 
-    if (! body)
+    if (body == nullptr)
         return;
 
     body->traverse(&it);