Clean up the mousewheel prefs so that the Boxes and Springs are the same

for each option in the dropdown box, and the text doesn't jump around when
you change it.  r=sspitzer.

suite/common/pref/pref-mousewheel.xul

@@ -110,13 +110,11 @@
             <html:input type="text" id="mousewheelWithAltKeyNumlines" size="3" pref="true" preftype="int" prefstring="mousewheel.withaltkey.numlines"/>
             <html:label>&scrollLines.label;</html:label>
           </box>
-          <box orient="horizontal">
             <html:div>
               <html:input type="checkbox" id="mousewheelWithAltKeySysNumlines" pref="true" preftype="bool" prefstring="mousewheel.withaltkey.sysnumlines"
                           onclick="doEnableElement( this, 'mousewheelWithAltKeyNumlines' );"/>
-            </html:div>
             <html:label for="systemDefault">&useSystemDefault.label;</html:label>
-          </box>
+            </html:div>
         </box>
         <spring flex="1"/>
       </box>
@@ -125,6 +123,8 @@
           <html:input type="radio" name="actionRadioAltKey" id="mousewheelWithAltKeyAction1" pref="true" preftype="int" prefindex="1" prefstring="mousewheel.withaltkey.action"/>
           <html:label for="mousewheelWithAltKeyAction1">&scrollPgUpPgDn.label;</html:label>
         </html:div>
+
+      <spring flex="1"/>
       <!-- history back/fwd-->
         <html:div>
           <html:input type="radio" name="actionRadioAltKey" id="mousewheelWithAltKeyAction2" pref="true" preftype="int" prefindex="2" prefstring="mousewheel.withaltkey.action"/>
@@ -159,6 +159,8 @@
           <html:input type="radio" name="actionRadioCtrlKey" id="mousewheelWithCtrlKeyAction1" pref="true" preftype="int" prefindex="1" prefstring="mousewheel.withcontrolkey.action"/>
           <html:label for="mousewheelWithCtrlKeyAction1">&scrollPgUpPgDn.label;</html:label>
         </html:div>
+
+        <spring flex="1"/>
       <!-- history back/fwd-->
         <html:div>
           <html:input type="radio" name="actionRadioCtrlKey" id="mousewheelWithCtrlKeyAction2" pref="true" preftype="int" prefindex="2" prefstring="mousewheel.withcontrolkey.action"/>