PATCH: relax restrictions on per-architecture data registration

[Jim Blandy <jimb@zwingli.cygnus.com>]

I tested this on a multi-arch target, and it seemed to work, so I've
committed it.

Jim Blandy <jimb@cygnus.com> writes:
> This is supposed to fix G++ V3 on non-multiarch targets.  Not sure
> this is right yet, just posting for the curious.
> 
> 2001-06-01  Jim Blandy  <jimb@redhat.com>
> 
> 	Expand the gdbarch per-architecture data vector as needed, rather
> 	than requiring that all per-architecture data be registered before
> 	the first gdbarch object is allocated.
> 	* gdbarch.sh: Changes to effect the following:
> 	* gdbarch.c (alloc_gdbarch_data, init_gdbarch_data): Delete
> 	declarations and definitions.
> 	(check_gdbarch_data): New function, and declaration.
> 	(gdbarch_alloc): Don't call alloc_gdbarch_data; leaving the fields
> 	zero is good enough.
> 	(free_gdbarch_data): Tolerate a null data pointer.  Free only
> 	those data items gdbarch->data actually has allocated.
> 	(set_gdbarch_data, gdbarch_data): Call check_gdbarch_data.
> 	(gdbarch_update_p): No need to call init_gdbarch_data.