r16550: Fix bug 3866. Thanks for the report!

r16550: Fix bug 3866.  Thanks for the report!

Although I've never met a computer or compiler that produced pointers to
functions which are a different size than pointers to data, I suppose they
probably exist.  Assigning a pointer to a function is technically illegal in C
anyway.

Change casts of the option_value based on the option_name to use of variable
argument lists.

For binary compatibility, I've maintained but deprecated the old behavior of
debug_stderr (which expected to be passed a NULL or non-NULL pointer) and
added a new option debug_to_stderr which properly expects a boolean (int)
parameter.

Derrell
(This used to be commit c1b4c510530ca3118d1eccb9615a8cad732c7373)