[test] Always draw fresh histograms in stressGraphics.

In the past, stressGraphics was retrieving a histogram from a file,
modifying it and drawing it. In subsequent tests, the histogram is again
read from the TFile, but this returns the in-memory object. This means
that the previous tests influence the subsequent tests, e.g. whether or
not statistics objects are displayed.
In particular, subsequent tests will have the statistics box drawn
twice, once from THistPainter::PaintStat(), and once from the fact that
the box is added to the list of functions. This impacts output files
such as PDF/PS/SVG.

Here, the histogram is always cloned when it is retrieved from the file,
so the tests are independent. The reference files for SVG are
regenerated, because the statistics box is now only drawn once.
Similarly, the output size of the .ps files has been corrected to
reflect that the boxes are only drawn once.

Author: hageboeck

test/stressGraphics.cxx

@@ -2016,7 +2016,7 @@ void th2_cut()
    Float_t y[6] = { 2, 0, -2, -2,  0,  2 };
    TCutG *cut = new TCutG("cut", 6, x, y);
 
-   TH1 *hpxpy = (TH1*)gHsimple->Get("hpxpy");
+   TH1 *hpxpy = (TH1 *)gHsimple->Get("hpxpy")->Clone("th2_cut");
 
    hpxpy->Draw("col [cut]");
    cut->Draw("l");
@@ -3828,7 +3828,7 @@ void clonepad()
 {
    TCanvas *C = StartTest(700,500);
 
-   TH1 *hpxpy = (TH1*)gHsimple->Get("hpxpy");
+   TH1 *hpxpy = (TH1 *)gHsimple->Get("hpxpy")->Clone("hpxpy_clonepad");
    hpxpy->Draw();
    TCanvas *C2 = (TCanvas*)C->DrawClone();
 

test/stressGraphics.ref

@@ -30,8 +30,8 @@
     th1_palette     17056       100     32429       100     29162     12000     35018     15000     17487       300
        thstack1     30815       100     28522       100     46061     15000     23026     10000     31035       100
         th2_cut     14774       600     16179       300     19511      5000     11533      4000     16039       600
-     th2_candle    113353      1000     71394       500    136880     40000     51345     20000    115314      1000
-     th2_violin     73316       500     84161       500     85037     20000     34733     15000     73223       500
+     th2_candle    102431      1000     71394       500    136880     40000     51345     20000    115314      1000
+     th2_violin     67738       500     84161       500     85037     20000     34733     15000     73223       500
    th2_axlabels      4878       600     14375       100     17419      5000     11709      1800      5770       600
       th2_stats     27107       300     19227       300     30587     14000     16531      7000     27039       500
        tellipse      4131        40     15272       100     34038      2500     12258      1400      4162        40