Bug 1641226

Description of problem:
In gfdb_sqlite3.h, there's the definition:
#define GF_SQL_COMPACT_DEF GF_SQL_COMPACT_INCR

This makes lot of other code, which compares GF_SQL_COMPACT_DEF to other values, quite useless.
For example, in gfdb_sqlite3.c, the whole switch is useless:
            ret = 0;
            switch (GF_SQL_COMPACT_DEF) {
                case GF_SQL_COMPACT_FULL:
                    ret = gf_sqlite3_set_pragma(db_conn, "auto_vacuum",
                                                GF_SQL_AV_FULL);
                    break;
                case GF_SQL_COMPACT_INCR:
                    ret = gf_sqlite3_set_pragma(db_conn, "auto_vacuum",
                                                GF_SQL_AV_INCR);
                    break;
                case GF_SQL_COMPACT_MANUAL:
                    changing_pragma = _gf_false;
                    break;
                default:
                    ret = -1;
                    gf_msg(GFDB_STR_SQLITE3, GF_LOG_ERROR, 0,
                           LG_MSG_COMPACT_FAILED, "VACUUM type undefined");
                    goto out;
                    break;
            }

It's quite clear where it'll go. The rest is dead code. As such, the compiler complains that the initial 'ret = 0' is not needed - this value set to 'ret' is never read - which is true, as the switch goes to:
ret = gf_sqlite3_set_pragma(db_conn, "auto_vacuum",
                                                GF_SQL_AV_INCR);