verifies EBNF productions are consistent and grammatically correct

 Ebnflint verifies that EBNF productions are consistent and grammatically
 correct. It reads them from an HTML document such as the Go specification.
 .
 Grammar productions are grouped in boxes demarcated by the HTML elements
 .
   <pre class="ebnf">
   </pre>
 .
 Usage:
 .
   ebnflint [--start production] [file]
 .
 The --start flag specifies the name of the start production for the grammar; it
 defaults to "Start".