There are internal types that are unbounded arrays. Allow subtype
syntax that creates bounded versions of these arrays, and elaborate
them as vectors at port boundaries. This makes some interesting types
work out.
Also start replacing vhdlint and vhdlreal with int64_t and double,
which are reasonable values for universal_integer and universal_real
from the VHDL standard. I need these cleaned up because the ints in
particular are used for the literal expressions in array index constraints.
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.
Elaboration will need a parse tree for expressions. Create one for
the expression types that are currently supported. Also add rules
and the keywords for all the remaining binary logical operators.