[doc] gettext printf_conversion mprintf msprintf mfprintf pages updated & fixed

[doc] gettext printf_conversion mprintf msprintf mfprintf pages updated & fixed

  * update for numbered placeholders "%n$"
  * update for boolean input
  * printf_conversion fixed for many issues (see changes), and a lot improved.
    I think that when processing the bug http://bugzilla.scilab.org/5511 10 years ago,
    the uploaded XML were not the right ones: there were so many issues left...
    (or i was more lazy :-/ )

    Bundled PDF: http://bugzilla.scilab.org/attachment.cgi?id=5260

Change-Id: I755f6fa53140e3a357a55188d16ff36288c1fc8f