Add .hgignore file.
List all generated or temp files in .hgignore, so they
don't clutter the screen when running hg status.
(transplanted from befdb88324e18e1e80260906d0459a56ea0eb37a)
1 This is NOT the official version of dialog. This version has been
2 significantly modified from the original. It is for use by the Linux
3 kernel configuration script. Please do not bother Savio Lam with
4 questions about this program.