[bash] Add `diff' function for colorized paged output in a terminal.
[bash] Do not hardcode script name in `fhelp' function.
[bash] Fix `fhelp' function for overlapping function names.
[bash] Fix `print_header' function to recompute color sequences on each invocation.
[bash] Produce unified diffs.
[bash] Fix return value of `diff' function.
[emacs] Customize comment highlighting (emacs 22.2 fix).