Use noinst_LTLIBRARIES for internal and yparser to make unified libknot.

Make internal and yparser convenient libraries (noinst_LTLIBRARIES)
and link them only where needed.  Some of the code will get linked
twice into the binary, but that's inevitable unless we want to keep
exporting volatile symbols library to the outside world.

(Or we can cleanup usage of libknot-internal outside libknot and perhaps libknotd.)