connection_test: Added a simple test for sdb_connection_accept().
core: Don't leak memory when shutting down the collector loop.

Instead, put the current collector object back into the list in oder to keep a
reference to it.
core: Don't leak memory upon an error in the collector loop.
frontend: FETCH, LIST, LOOKUP are untyped tokens.
frontend: Fixed deprecated %name-prefix syntax.
frontend: Added destructors for dynamically allocated objects in the parser.

This will make sure that the memory is freed in case of parse errors.
Merged branch 'master' of git://git.tokkee.org/sysdb.