make -threads a developer option
remove file name from error messages

While a GtBioseq can have a file name, this is not the
case for any implementation of the GtSeqCol. This commit
removes file names from the respective error messages
to avoid getting "(null)" as a file name.
update SQLite to 3.8.2
remove SQLite from the amalgamation
Merge pull request #169 from satta/clean

minor compiling fixes, SQLite update, error message fix