Move registry to interp and add support for functions and filesystems.
This will be used later for allow formats to add own functions and fq code.
Add gojqextra function helpers to have more comfortable API to add functions.
Takes care of argument type casting and JQValue:s and some more things.
Refactor interp package to use new function helper and registry. Probably
fixes a bunch of JQValue bugs and other type errors.
Refactor out some mpeg nal things to mpeg format.
Refactor interp jq code into display.q and init.jq.
Remove undocumented aes_ctr funciton, was a test. Hopefully will add more crypto things laster.
repl now rewrites query to do implicit display inside the sub eval.
This makes it possible to interrupt eval and output in a better and faster way.
Make JSON encoder fail early on errors.
Add more interrupt tests.
Now repl, slurp and help implemented using same query rewrite.
Include filename context in error if possible.
Add spew function that does opposite of slurp.
Start of help infra, not done or documented yet.
Show error pointer on parse error.
Rename internal eval to _eval and make eval be wrapper that
does rewrite and has various eror handling etc.
Nicer repl, slupr and help errors.
