Rework the handling of file names to use a perm_string heap to hold
the file names, instead of the custom file name heap in the lexor.
Also rename the get_line to get_fileline to reflect its real duties.
This latter chage touched a lot of files.
location of things. PGate, Statement and PProcess.
elaborate handles module parameter mismatches,
missing or incorrect lvalues for procedural
assignment, and errors are propogated to the
top of the elaboration call tree.
Attach line numbers to processes, gates and
assignment statements.