update for make GHDL: analyze package files first
 * bugfix in test_structural.py
 * added test_structural.py in Makefile
support for user-defined code and top-level enumerations.
 * User-defined code generate component file and declaration.
 * Top-level enumeration generate separate package file.
conversion bugfix: unused signals
bugfix in KH test for GHDL
support for Modelsim in tests
support for Modelsim in tests
add test_unused.py