better handle parameters with long identifiers

[SVN r25385]

doc/html/boostbook.css

@@ -86,10 +86,14 @@ div.variablelist dl dt
 {
    float: left;
    clear: left;
-   width: 10%;
    font-style: italic;
 }
 
+div.variablelist dl dd
+{
+   padding-left: 8pc;
+}
+
 @media screen
 {
    a{ color: blue; }