Remove support for compact portaudit file
Use nested transaction to update remote schema

Otherwise it commit/rollback in the end of the transaction will close
the transaction initiated by pkgdb_repo_init()
Be consistent about stdout/stderr in pkg.

If a user requires `pkg help` explicitly then we output help strings
to stdout. Otherwise, we use stderr assuming that a user doesn't know
what to do with pkg.

Closes:	#695
Submitted by:	jmmv
Stop linking to ncurses
Fix rotten repo-*.sqlite when ^C is hit
Be more clever about usage output.

If a user runs `pkg` without arguments suggest to use `pkg help`.
If a user types `pkg help` then show the full help and exit with exit
code 0.
If a user makes errors in arguments or commands, display an error and
suggest to run `pkg help`.

Closes:	#696
Reported by:	jmmv