Program Model – Line Info List

As good practice, the changes to implement the error highlighting will be made in small increments.  The first was to replace the program model's list of translated lines (pointers to RPN lists) with he list of line information items, each containing a pointer to the RPN list for the line (for now until the encoder is implemented) and an index to the error list if the line as an error (for now not used).

This change was trivial and just amounted to adding the definition of the LineInfo structure, private to the ProgramModel class since will be the only user of this structure; and changing the uses of the translated lines list member with the line information list member.

[commit aee559d041]