#427 [ucsim] CDB/var handling improvements

[Mike Jagdis]

When parsing CDB files we only care about the 'L' records - they have everything we need
For file and function scoped symbols we add them keeping the ":Fname$" and ":Lname$" prefixes to ensure they stay unique
If output of "info var" is redirected to a .cdb file we output only the user or CDB added vars using CDB 'L' records so they can be reloaded in a later session