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.

--- a/test/bug-53027/bug-53027.tst	Sun Nov 27 16:58:42 2022 -0500
+++ b/test/bug-53027/bug-53027.tst	Sun Nov 27 17:01:00 2022 -0800
@@ -1,18 +1,18 @@
 %!function load53027 (fname)
-%!  global X
+%!  global X;
 %!  X = 2;
 %!  load (fname);
 %!  assert (X, 1);
 %!endfunction
 
 %!function save53027 (fname)
-%!  global X
+%!  global X;
 %!  X = 1;
 %!  save (fname, "X");
 %!endfunction
 
 %!test <*53027>
-%! global X
+%! global X;
 %! X = 0;
 %! fname = tempname ();
 %! save53027 (fname);