Adds (most) configure switches to menuselect. The defaults are _not_
changed, meaning the default configuration itself remains the same.

This enables changing the configuration through menuselect and adds
flags that other packages may use.

Config.in is renamed to Config-lib.in in anticipation of a future commit
where the cli tool package also gets a file to source.

The variables also get a prefix change from SQLITE to SQLITE3 in case
there will be a new major release in the future that may coexist with
sqlite3.

Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>