Make the synopsis the same size as other code blocks

[SVN r62295]

doc/src/boostbook.css

@@ -39,7 +39,7 @@
 
     pre.synopsis
     {
-        font-size: 90%;
+        font-size: 9pt;
         margin: 1pc 4% 0pc 4%;
         padding: 0.5pc 0.5pc 0.5pc 0.5pc;
     }