* amd64-tdep.c (amd64_convert_register_p): Delete.

	* amd64-tdep.c (amd64_convert_register_p): Delete.
	(amd64_init_abi): Use i387_convert_register_p.
	* alpha-tdep.c (alpha_convert_register_p): Return zero for
	eight byte types.
	(alpha_register_to_value, alpha_value_to_register): Do not handle
	eight byte types.
	* i386-tdep.c (i386_convert_register_p): Use i387_convert_register_p.
	* i387-tdep.c (i387_convert_register_p): New.
	(i387_register_to_value, i387_value_to_register): Update comments.
	* i387-tdep.h (i387_convert_register_p): Declare.
	* ia64-tdep.c (ia64_convert_register_p): Return zero for
	builtin_type_ia64_ext.
	(ia64_gdbarch_init): Do not initialize builtin_type_ia64_ext here.
	(_initialize_ia64_tdep): Initialize builtin_type_ia64_ext here.
	* m68k-tdep.c (m68k_convert_register_p): Return zero for
	builtin_type_m68881_ext.
	(m68k_register_to_value, m68k_value_to_register): Update comments.

	* gdbint.texinfo (Register and Memory Data, Target Conditionals):
	Document that gdbarch_convert_register_p should return zero for no-op
	conversions.