Marginal improvement parsing templates in definition lists

 * Example 1, ;{{echo|''a:b''}} now properly becomes
     <dl><dt><i>a:b</i></dt></dl>
   as opposed to what we have now
     <dl><dt>{{echo|''a</dt><dd>b''}}</dd></dl>

 * Example 2, ;{{echo|a:b}} is rather unfortunate. Currently
     <dl><dt>{{echo|a</dt><dd>b}}</dd></dl>
   but with this change
     <dl><dt>a:b</dt></dl>
   when it should be
     <dl><dt>a</dt><dd>b</dd></dl>

 * Should look into adding an inList flag while tokenizing fetched
   templates that pushes a colon on the stack.

Change-Id: Icd0b89c50d137b045171d126ddb6848a8aacb06a