fix backward compatibility problem with using_toolkit
fix backward compatibility problem with using_toolkit

using_toolkit was not properly supported in imported
task libraries, which would led to errors related to
dynamic linking. The error case was:

 TK is defined in A
 TK is imported in B
 B is imported in C, and a deployment uses tasks defined in B

Then C would *not* be linked to TK if B used using_toolkit instead
of import_types_from. This commit fixes that problem.

doudou/modelkit-component,doudou/modelkit-component