* gdbarch.sh (gcore_bfd_target): New gdbarch callback.
* gdbarch.h, gdbarch.c: Regenerate.
* gcore.c (default_gcore_target): Make return value const.
Call gdbarch_gcore_bfd_target if present.
(default_gcore_arch, default_gcore_mach): Use target_gdbarch.
* corelow.c (core_read_description): Call gdbarch_core_read_description
on core_gdbarch instead of current_gdbarch.