Release checklist for Tux Paint

Places to make sure version # and release date gets updated, prior to
cutting a release (tagging in the source code repository, and running
"make release" to roll a .tar.gz source tarball).

 * Makefile

 * Build description files:
   * tuxpaint.spec (RPM package)
   * macos/Info.plist (macOS build)

 * Documentation
   (For HTML variants, be sure to run "make" in "docs/", to
   produce plaintext alternatives!)

   * docs/CHANGES.txt
   * docs/en/html/README.html
   * docs/en/html/FAQ.html
   * docs/en/html/OPTIONS.html
   * docs/en/html/EXTENDING.html
   * docs/en/html/ADVANCED-STAMPS-HOWTO.html

 * Manual page (manpage)
   * src/manpage/tuxpaint.1