kilo: I've started my own version of kilo

Based on the comments I've made so far, I've started my own version of kilo, which you can find here if you are interested.

I've chosen to make some different design and stylistic choices from the previous versions. Most notably, I just can't restrict myself to a single source file. Even for a relatively small project like this, it's just too claustrophobic. I've also chosen the Unix style of underscores in identifiers (editor_process_keypress) rather than camel case (editorProcessKeypress), which feels anachronistic to me in the C/Unix environment.

I've also created a simple Perl script to help deal with the string constant issue I've mentioned previously. This allows arcane terminal escape sequences to be named symbolically, with their length computed at compile time. I expect a decent C optimizer will generate very similar code to the original inline versions.

I've also renamed struct abuf to the typedef-ed term_buffer, so the erstwhile editorRefreshScreen looks like this in my implementation:

void editor_refresh_screen()
{
    term_buffer tb;
    tb_init(&tb);
    
    string_const home_cursor = get_home_cursor_str();

    tb_append_str(&tb, get_cursor_off_str());
    tb_append_str(&tb, home_cursor);

    editor_draw_rows(&tb);

    tb_append_str(&tb, home_cursor);
    tb_append_str(&tb, get_cursor_on_str());
    
    tb_write(&tb);
    tb_free(&tb);
}

The functions get_home_cursor_str(), get_cursor_off_str(), and so on are automatically generated by my Perl script linked above. Notice how much nicer this is than the version shown in step 40:

void editorRefreshScreen() {
  struct abuf ab = ABUF_INIT;

  abAppend(&ab, "\x1b[?25l", 6);
  abAppend(&ab, "\x1b[2J", 4);
  abAppend(&ab, "\x1b[H", 3);

  editorDrawRows(&ab);

  abAppend(&ab, "\x1b[H", 3);
  abAppend(&ab, "\x1b[?25h", 6);

  write(STDOUT_FILENO, ab.b, ab.len);
  abFree(&ab);
}