[treeplayer] Explicitly add TEventList/TEntryList to gDirectory.

The TTree::Draw documentation states that entry lists and event lists
are added to gDirectory. To make this fact independent of ROOT 7 mode,
explicitly add instances of these classes to gDirectory.

Also add a warning when trying to append to an existing list that can't
be found in the current directory.

Author: hageboeck

tree/treeplayer/src/TSelectorDraw.cxx

@@ -405,11 +405,16 @@ void TSelectorDraw::Begin(TTree *tree)
                return;
             }
             if (!enlist) {
+               if (hnameplus) {
+                  Warning("TSelectorDraw", "TTree::Draw was asked to append to TEntryList '%s', but it was not found in the current directory."
+                     "Did you forget to call entryList->SetDirectory(gDirectory) or similar? Creating a new list now.", hname);
+               }
                if (optEnlistArray) {
                   enlist = new TEntryListArray(hname, realSelection.GetTitle());
                } else {
                   enlist = new TEntryList(hname, realSelection.GetTitle());
                }
+               enlist->SetDirectory(gDirectory); // TTree::Draw documentation promises it shows up in gDirectory
             }
             if (enlist) {
                if (!hnameplus) {
@@ -421,6 +426,7 @@ void TSelectorDraw::Begin(TTree *tree)
                      } else {
                         inElist = new TEntryList(*enlist);
                      }
+                     inElist->SetDirectory(gDirectory); // TTree::Draw documentation promises it shows up in gDirectory
                      fCleanElist = true;
                      fTree->SetEntryList(inElist);
                   }
@@ -444,7 +450,12 @@ void TSelectorDraw::Begin(TTree *tree)
                return;
             }
             if (!evlist) {
+               if (hnameplus) {
+                  Warning("TSelectorDraw", "TTree::Draw was asked to append to TEventList '%s', but it was not found in the current directory."
+                     "Did you forget to call eventList->SetDirectory(gDirectory) or similar? Creating a new list now.", hname);
+               }
                evlist = new TEventList(hname, realSelection.GetTitle(), 1000, 0);
+               evlist->SetDirectory(gDirectory); // TTree::Draw documentation promises it shows up in gDirectory
             }
             if (evlist) {
                if (!hnameplus) {