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 reporter_name="unknown"
2 reporter_url="http://iphonelinux.org/index.php/Glibc_toolchain_using_crosstool-NG"
3 reporter_comment="An (experimental) toolchain targeting the Apple's iPhone."