gdbarch-ification of ravenscar-thread support.

gdbarch-ification of ravenscar-thread support.

gdb/ChangeLog:

        * gdbarch.sh: Add "struct ravenscar_arch_ops" advance
        declaration.
        (ravenscar_ops): New gdbarch variable.
        * gdbarch.h, gdbarch.c: Regenerate.
        * ravenscar-thread.h (ravenscar_register_arch_ops): Delete.
        * ravenscar-thread.c (current_arch_ops): Delete.
        (ravenscar_fetch_registers): Get the ravenscar_arch_ops
        from the gdbarch.
        (ravenscar_store_registers, ravenscar_prepare_to_store): Likewise.
        (ravenscar_inferior_created): Add gdbarch_ravenscar_ops check.
        (ravenscar_register_arch_ops): Delete.
        * ravenscar-sparc-thread.h: New file.
        * ravenscar-sparc-thread.c: #include "ravenscar-sparc-thread.h".
        (ravenscar_sparc_ops): Define value statically.
        (_initialize_ravenscar_sparc): Delete.
        (register_sparc_ravenscar_ops): New function.
        * sparc-tdep.c: #include "ravenscar-sparc-thread.h".
        (sparc32_gdbarch_init): Add call to register_sparc_ravenscar_ops.
        * Makefile.in (ALL_TARGET_OBS): Add ravenscar-thread.o and
        ravenscar-sparc-thread.o.
        (SFILES): Add ravenscar-thread.c.
        (HFILES_NO_SRCDIR): Add ravenscar-sparc-thread.h.
        (ALLDEPFILES): ravenscar-sparc-thread.c.
        * configure.tgt: Add ravenscar-thread.o and ravenscar-sparc-thread.o
        to gdb_target_obs
        for all the targets that use sparc-tdep.o.