doc: Add undocumented functions to Octave manual for 8.1 release. * basics.txi: Add DOCSTRING entry for "cmdline_options". Correct missing word in description of "--built-in-docstrings-file" commmand line option. Wrap some lines to 80 characters. * mk_undocumented_list: Add exceptions to undocumented list for ytickangle, ztickangle. * octave.cc (Fcmdline_options): Improve documentation string. Add BIST tests. * octave.cc (Fprogram_invocation_name, Fprogram_name): Improve documentation string. Check for pattern "Invalid call" in BIST error tests for input validation.