Remove types and functions only needed for VHDL < 2008

[Paebbels]

VHDL-2008 added many new datatypes (integer_vector, boolean_vector, ...) and related functions and operators. PoC reimplemented them for VHDL-93 environments.

• Check what's needed and what can be dropped.
• Check if VHDL-93 code could be hidden in a conditional analysis block or second package.