luasql: New package

Luasql is a uniform frontend for multiple DB backends.

[Thomas P: update version to 2.3.0 available from Github, as suggested
by François Perrad. Fix .mk header. Use a LUASQL_MAKE_FLAGS variable,
which is more commonly used.]

Signed-off-by: Assaf Inbal <shmuelzon@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>