When a function is declared and named with the blank identifier, only
    the syntax is checked.  This patch modifies the parser to add a dummy
    node for each function declaration with a blank identifier name that
    will be type checked like any function declaration.
    
    Fixes golang/go#11535.
    
    Reviewed-on: https://go-review.googlesource.com/13792

From-SVN: r227160