use pixel font sizes

the qt layout system is pixel-based, so using point sizes doesn't work
for anyone with a different resolution (DPI) than me

src/plugins/coreplugin/welcomemode.ui

@@ -26,7 +26,7 @@ background-color: qlineargradient(spread:pad, x1:0.5, y1:0, x2:0.5, y2:1, stop:0
 
 *, * *, * * *, * * * *, * * * * * {
 font-family: Arial, Trebuchet, Lucida, sans-serif;
-font-size: 9pt;
+font-size: 12px;
 color: #5e5e5e;
 }
 
@@ -118,7 +118,7 @@ border-width: 8 8 8 8;
             <property name="text">
              <string>&lt;style&gt;
 h1 {
-    font-size: 2em;
+    font-size: 24px;
     font-weight: normal;
     color: #4d4d4d;
     margin-top: 0px;