Strip down essential WITH-YACLML-* functionality, nothing more

* yaclml.asd (:yaclml): Removed src/tal module.
(:yaclml.test): Depend on :stefil, not FiveAM
(perform): No need for most of these ASDF:PERFORM hooks, though
maybe the one that runs tsts after loading the system might be
nice. Left it commented..
(ensure-system-has-feature): Delete.

* src/packages.lisp (:it.bese.yaclml): Removed exports for TAL.
(:it.bese.yaclml.tal): Removed TAL package.

* src/yaclml.lisp (*tal-truename*,*xml-reader-open-char*)
(*xml-reader-close-char*)
(enable-xml-syntax, %enable-xml-syntax, xml-reader-open)
(with-xml-syntax): Delete
Add .gitignore