* Bugs 16438 16685: asciimat(text) fixed + various lengths + UTF8

* Bugs 16438 16685: asciimat(text) fixed + various lengths + UTF8

  asciimat() proposed page (PDF): http://bugzilla.scilab.org/attachment.cgi?id=5266

  http://bugzilla.scilab.org/16438 :
    Support to strings of distinct lengths added.
    Support to strings including UTF8 extended characters added.
  http://bugzilla.scilab.org/16685 :
    asciimat(['ab';'';'ab']) result was wrongly shaped.
    asciimat(['a';'';'b']) yielded an error.
    asciimat(stringHypermat) squeezed dim#2 of the result and so
                             did not cope with Matlab/Octave's behavior.
  test_run string asciimat
  test_run string bug_14976
  test_run statistics histc

  To keep track of its files changes, asciimat() will be moved in [m2sci] only later.

  In addition, an option could be implemented later, to make asciimat(text)
  fully working in an elementwise way (as first proposed @
  https://codereview.scilab.org/21566 )

Change-Id: I3183fc3d05491066816034802e8f09645261d76e