Documentation justification for hand coded shortcut.

To handle 'Float_t*', quickFindType uses no memory (instead of 183B for findType) and is much faster
(6 times in this case), the cost is the additional ('unnecessary') checks in the cases not handled by
quickFindType.

lib/Interpreter/LookupHelper.cpp

@@ -451,6 +451,9 @@ namespace cling {
     if (typeName.empty()) return TheQT;
 
     // Deal with the most common case.
+    // Going through this custom finder is both much faster
+    // (6 times faster, 10.6s to 57.5s for 1 000 000 calls) and consumes
+    // infinite less memory (0B vs 181 B per call for 'Float_t*').
     QualType quickFind;
     if (quickFindType(typeName,quickFind, *m_Parser, diagOnOff)) {
       // The result of quickFindDecl was definitive, we don't need