perl script to generate single hoc file out of multiple hoc files

reads load_file() statements in a hoc file to create 
a single hoc output file with loaded hoc code inserted in place of the load_file statements

uses HOC_LIBRARY_PATH to locate files

several options available -- call without args for help

limitations: 
1. does not read xopen() commands
2. does not process 2 arg load_file() command
3. cannot handle a load_file() embedded in an 
if {} or other other control structure (this requires logical parsing of the whole file as can only be done by hoc parser) -- will generate an error