ugtrain: introduce dynval from cfg entry support

We already have it for the checks that we can read a value not from
an address but instead from a cfg entry. So let's do the same for
DYN_VAL_ADDR!

Example: Warzone 2100: read the max. build points for a Structure
         from Structure stats
ugtrain: unify type conversion style

This is minor: Just add a space after the type conversion where it
is missing for better readability.