Use arch-independent format string for guint64 in tests

Otherwise "0" is printed out even if the right number is returned by the tested
function.
Fix running tests so that local builds are used
Add and move includes to where they are actually needed

Only tests need prints there's no point in including header header files in the
tested code itself.
Add type-wise return values to stub functions

This makes compiler much happier.
Reorder requirements of the test-library target

Don't know if 'make' preserves the order in all cases, but thy should be ordered
logically at least.
Check if plugins were loaded to get library's init status

The initialization of the library is just initialization of its plugins. The
status of library initialization should reflect that.
Add target for running ipython with the library available

Some environment variables need to be set properly in order to make ipython find
all the data to load the library.
First function for the swap plugin