move packages disabled since 3.13 to unmaintained
if nobody fixed build (let alone run) in 6 months, they are de facto unmaintained.
also move emscripten-fastcomp since it is only used for emscripten according to APKBUILD comments.
roughly based on this script:
git checkout v3.13.0
grep -l 'arch=""' */*/APKBUILD > 3.13
git checkout master
grep -l 'arch=""' */*/APKBUILD > master
comm -12 3.13 master | cut -d / -f 1-2 | xargs -I{} git mv {} unmaintained/
closes #10402 (closed), #10995 (closed).
cc who disabled these packages: @kaniini @Leo @kdaudt @Cogitri @mps
cc listed contributors/maintainers: @clandmeter @ernierasta @jirutka @vaka @ed @fabled @ncopa @gjabell @azarus @daniel @bl4ckb0ne @terra @jjsearle @pickfire @ddevault