* init.c (scm_start_stack): Don't initialize scm_progargs here.

* init.c (scm_start_stack): Don't initialize scm_progargs here.
(scm_boot_guile): Call scm_set_program_arguments here, later than
the old initialization.

* init.c: (scm_boot_guile, scm_boot_guile_1):  New, simplified
initialization procedure.
- Delete in, out, err arguments; there are other perfectly good
ways to override these when desired.
- Delete result argument; this function shouldn't ever return.
- Rename init_func argument to main_func, for less confusion.
- Delete boot_cmd argument; main_func is more general.
-Add 'closure' argument, to help people pass data to main_func
without resorting to global variables.
- Abort if reentered; don't bother returning an error code.
- Call scm_init_standard_ports to set up the default/current
standard ports; no need to pass them to scm_start_stack.
- Remove code to evaluate the boot_cmd, and start the repl; let
the user do something like that in main_func if they want.
- Remove code to package up a return value; main_func can do any
of that as needed.
- Call exit (0), instead of returning.
(scm_start_stack): Don't initialize the I/O ports here; that's
weird.  Delete in, out, err arguments.  Move guts to
scm_init_standard_ports, scm_stdio_to_port.
(scm_init_standard_ports): New function, to set up current and
default standard ports.
(scm_start_stack, scm_restart_stack): Make these static.
* init.h (scm_boot_guile): Adjust declaration.
(scm_start_stack, scm_restart_stack): Remove externally
visible declarations for these.
(enum scm_boot_status): Removed; now scm_boot_guile never returns.