Implement the parser infrastructure for handling library use clauses,
and use that to handle specific packages of the ieee library. Make
the numeric types come from the numeric_* packages instead of being
built in.
Rather then leave net types to implicit declarations, write
declarations explicitly. This will become necessary when more
interesting types are supported.
Separate elaboration from code generation in the Entity, and add
to Architectures a code generator to handle some simple cases. At
this point we have the basic structure for the VHDL compiler.
Stephen Williams