In nets, if system functions return a real value the function lookup
was getting the correct width, but was also setting the width to 0,
which confused down-stream net handling. Real-value system fuctions
have a width of 1. (1 real-valued scalar.)
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.
Stephen Williams
steve