maint: Use "FIXME:" coding convention in m-files. * flipdim.m, prepad.m, rotdim.m, doc.m, strread.m, textread.m, krylov.m, colon.m, dump_prefs.m, fileattrib.m, getappdata.m, __xzip__.m, unpack.m, fsolve.m, axis.m, meshc.m, print.m, __ghostscript__.m, __go_draw_axes__.m, __print_parse_opts__.m, struct2hdl.m, unique.m, spstats.m, treeplot.m, test.m, datestr.m: Use "FIXME:" coding convention in m-files.

--- a/scripts/general/prepad.m
+++ b/scripts/general/prepad.m
@@ -97,7 +97,7 @@
 %!assert (prepad ([1,2], 2, 2, 3), reshape ([2,2,1,2], 1, 2, 2))
 %!assert (prepad ([1;2], 2, 2, 3), reshape ([2;2;1;2], 2, 1, 2))
 
-## FIXME -- we need tests for multidimensional arrays.
+## FIXME: We need tests for multidimensional arrays.
 
 %!error prepad ()
 %!error prepad (1)