* symtab.h: (struct symbol_register_ops): New struct definition.
(struct symbol): Make "ops" member a union of symbol_computed_ops and
symbol_register_ops callback pointers.
(SYMBOL_REGISTER_OPS): New macro.
* tracepoint.c: Include "objfiles.h".
(scope_info, collect_symbol): Use SYMBOL_REGISTER_OPS register_number
callback to retrieve register numbers.
* ax-gdb.c (gen_var_ref): Likewise.
* findvar.c (read_var_value): Likewise.
* printcmd.c (address_info): Likewise.
* coffread.c (coff_reg_to_regnum): New function.
(coff_register_funcs): New static variable.
(process_coff_symbol): Do not call gdbarch_sdb_reg_to_regnum.
Install SYMBOL_REGISTER_OPS callbacks.
* mdebugread.c (mdebug_reg_to_regnum): New function.
(mdebug_register_funcs): New static variable.
(parse_symbol): Do not call gdbarch_ecoff_reg_to_regnum.
Install SYMBOL_REGISTER_OPS callbacks.
* stabsread.c (stab_reg_to_regnum): New function.
(stab_register_funcs): New static variable.
(define_symbol): Do not call gdbarch_stab_reg_to_regnum.
Install SYMBOL_REGISTER_OPS callbacks.