Add vpiIterator and vpiMemory to string version of vpiType
Add vpiIterator and vpiMemory to string version of vpiType

This patch adds both vpiIterate and vpiMemory to the list of
types that can be displayed as strings.

themperek/iverilog,CastMi/iverilog,themperek/iverilog,themperek/iverilog,CastMi/iverilog,CastMi/iverilog