Base class for Z-code parsers.
A Parser reads and parses a Z-code file into a big Perl hash.
For finding where the subroutines start and end, you can either depend on an external call to txd, a 1992 C program, or a beta pure Perl version.
Everything else is done in pure Perl.
Base class does nothing with args
If the input filename is not found AND the user did not enter, e.g., '.z5' at the end of the filename, the system will try to find a file ending with .z[1-9] or .dat.
Multiple or no matches -> return false
Reads the given Z-code file into memory
Parse Z-code header.
Creates %Constants, which stores a bunch of constants like the Z version number, where in memory things are stored, etc.
