Various people (among others Maxim Belooussov and Carsten Kunze)

Various people (among others Maxim Belooussov and Carsten Kunze)
reported that the build system still assumed that ohash is only
needed if sqlite3 is also in use, which is no longer true:
The ohash library is now required no matter what.

Rework sqlite3 and ohash library autodetection
such that both work independently of each other.
Provide LDADD for additional linker flags.
Add some missing variables to configure.local.example.