Add links to small versions of the screenshots

doc/gmsh.html

@@ -253,13 +253,17 @@ e-mails to send questions or bug reports.
 <h2>Gallery</h2>
 
 Everybody loves screenshots... So here are some:
-<A href="/gmsh/gallery/screenshot1.gif">screenshot 1</a>,
-<A href="/gmsh/gallery/screenshot2.gif">screenshot 2</a>,
-<A href="/gmsh/gallery/screenshot3.gif">screenshot 3</a>,
-<A href="/gmsh/gallery/screenshot4.gif">screenshot 4</a>.
-<p>
+<A href="/gmsh/gallery/screenshot1.gif">screenshot 1</a> 
+(<A href="/gmsh/gallery/screenshot1-small.gif">small</a>),
+<A href="/gmsh/gallery/screenshot2.gif">screenshot 2</a>
+(<A href="/gmsh/gallery/screenshot2-small.gif">small</a>),
+<A href="/gmsh/gallery/screenshot3.gif">screenshot 3</a>
+(<A href="/gmsh/gallery/screenshot3-small.gif">small</a>),
+<A href="/gmsh/gallery/screenshot4.gif">screenshot 4</a>
+(<A href="/gmsh/gallery/screenshot4-small.gif">small</a>).
 
-Some pictures made with Gmsh:
+<p>
+Some other pictures made with Gmsh:
 <ul>
 <li>Part of a shoulder bone:
     <A href="/gmsh/gallery/shoulder1.gif">pict1</a>,