Check db version before creating SQL functions

[mattmundell]

What:

Do the db version check before creating the SQL functions.

Why:

"CREATE OR REPLACE FUNCTION" fails if an argument name changes and the body of the function changes. In this case the migrator needs to be run before the "CREATE OR REPLACE FUNCTION", so we have to check the versions first.

How:

1. Modify "level_min_severity" in manage_pg.c:

• rename arg lvl to level
• add a new CASE with some random name.

2. restart gvmd
3. gvmd.log should have a database is wrong version log, and not a PQexec failed: ERROR: cannot change name of input parameter “lvl” log.

Checklist:

• Tests
• CHANGELOG Entry