testing/freedoom: upgrade to 0.13.0, take maintainership

https://freedoom.github.io/#freedoom-0.13.0

• Rebuild deutex with png support, which is required for freedoom to build
• Remove unneeded PIL patch, change has been upstreamed
• No tar.xz release archive was made available for this version, this seems to have happened before in some versions. Change source url to github archive tarball.
• make tries to use asciidoctor-pdf (missing package, which requires a number of runtime dependencies not yet available in the repos) to convert manual .adoc to .pdf, and while it gives an error, it does not seem to prevent the build from completing. Noticed the previous version of freedoom-doc did not contain the manual pdf either, but in the interest of making it available to users in the -doc package, copied it from the manuals release archive. If this step is unnecessary, please let me know and it can be removed.

Checked application launches with chocolate-doom in armv7.

Thanks!

cc: @Saijin-Naib

Update: revised MR to take up maintainership of both freedoom and deutex (unmaintained) per #alpine-devel conversation.