Make available some unix system calls to the interpreter
int SLang_init_slunix (void)
The SLang_init_slunix function initializes the interpreter's
unix system call intrinsic functions and makes them available to the
language. Examples of functions made available by
SLang_init_slunix include chmod, chown, and
stat_file. It returns 0 if successful, or -1
upon failure.
This function must be called after SLang_init_slang. It adds
the preprocessor symbol __SLUNIX__ to the interpreter.
SLang_init_slang, SLang_init_slfile, SLang_init_slmath