Execute a user or intrinsic function
int SLang_execute_function (char *fname)
This function may be used to execute either a user-defined function
or an intrinisic function. The name of the function is specified
by fname. It returns zero if fname is not defined, or
1 if the function was successfully executed, or -1 upon
error.
The function SLexecute_function may be a better alternative
for some uses.
SLang_run_hooks, SLexecute_function, SLang_is_defined