maint: cleanup code in BIST tests to use Octave coding conventions. * data.cc: Use keyword "endfor" rather than bare "end". * file-io.cc, graphics.cc: Remove semicolon ';' at end of "end_try_catch" keyword. * variables.cc, bug-35448.tst, bug-53027.tst, bug-53579.tst, bug-53599.tst, bug-53956.tst, bug-55758.tst, global.tst: Use semicolon ';' after "global" variable declaration. * for.tst, io.tst: Delete semicolon ';' at end of "for" loop declaration. * struct.tst: Delete semicolon ';' at end of "function" declaration.

%!function [raa, rbb, igaa, igbb] = sub1 (aa, bb)
%!  global aa bb;
%!  aa = 1;
%!  raa = aa;
%!  rbb = bb;
%!  igaa = isglobal ("aa");
%!  igbb = isglobal ("bb");
%!endfunction

%!test <*53579>
%! global aa bb;
%! assert (isglobal ("aa"));
%! assert (isglobal ("bb"));
%! aa = 3;
%! xx = 5;
%! [raa, rbb, igaa, igbb] = sub1 (aa, xx);
%! assert (raa, 1);
%! assert (rbb, []);
%! assert (igaa);
%! assert (igbb);
%! assert (xx, 5);
%! clear -global aa bb;  # cleanup after test