Add ports to the Sortix repository.

This change imports the ports collection from the former porttix and srctix
repositories and converts them to port(5) files with metadata pointing to
the upstream release tarballs with patches checked into this repository.
Ports are now developed and versioned along with the operating system and
are automatically built per the PACKAGES environment variable. The patches
are licensed under the same license as the relevant ports.

Tix has gained support for the new port(5) format. tix-port(8) is the new
high level ports build even point that handles downloading pstream releases
into the new mirror cache directory, applying the patches, building the port
with the lower-level tix-build(8), and finally installing the binary
package. The new tix-vars(8) program parses port(5) files and the new
tix-rmdiff(8) program produces input for tix-rmpatch(8).

The old doc/ directory is discontinued in favor of manual pages documenting
the new ports system.

The obsolete porttix-create(8) and srctix-create(8) programs are removed.

ports/libjpeg/libjpeg.port

@@ -0,0 +1,17 @@
+NAME=libjpeg
+BUILD_LIBRARIES=
+VERSION=9e
+DISTNAME=jpegsrc.v$VERSION
+COMPRESSION=tar.gz
+ARCHIVE=$DISTNAME.$COMPRESSION
+SHA256SUM=4077d6a6a75aeb01884f708919d25934c93305e49f7e3f36db9129320e6f4f3d
+UPSTREAM_SITE=https://ijg.org/files
+UPSTREAM_ARCHIVE=$ARCHIVE
+BUILD_SYSTEM=configure
+# TODO: Curiously, the programs shipped with libjpeg have the target name prefixed.
+CONFIGURE_ARGS='--program-prefix='
+MAKE_VARS='V=1'
+POST_INSTALL=tix-eradicate-libtool-la
+# TODO: The last letter is optional but sort -V before the first release.
+VERSION_REGEX='([0-9]+[a-z])'
+DISTNAME_REGEX=jpegsrc\.v$VERSION_REGEX