OpenDBX 1.3.1 released

This version enhances the library with a read-only large object interface, which enables access to blob and clob data stored within a database. The Firebird backend is the first one that implements this interface and is now able to fetch data objects up to several GB in size is smaller chunks. Along with the new interface, the code for the backends was split into several files, so it is more clearly arranged when extensions like the large object part will be added. Also, replacing stdint.h by the inttypes.h include removes an undesired dependency on automake from the header file.