* stdio-common/printf.h (struct printf_info): Add user element.

* stdio-common/printf.h (struct printf_info): Add user element.

	New types printf_arginfo_size_function, printf_va_arg_function.
	Declare register_printf_specifier, register_printf_modifier,
	register_printf_type.
	* stdio-common/printf-parse.h (struct printf_spec): Add size element.
	(union printf_arg): Add pa_user element.
	Adjust __printf_arginfo_table type.
	Add __printf_va_arg_table, __printf_modifier_table,
	__handle_registered_modifier_mb, and __handle_registered_modifier_wc
	declarations.
	* stdio-common/printf-parsemb.c: Recognize registered modifiers.
	If registered arginfo call failed try normal specifier.
	* stdio-common/printf-prs.c: Pass additional parameter to arginfo
	function.
	* stdio-common/Makefile (routines): Add reg-modifier and reg-type.
	* stdio-common/Versions: Export register_printf_modifier,
	register_printf_type, and register_printf_specifier for GLIBC_2.10.
	* stdio-common/reg-modifier.c: New file.
	* stdio-common/reg-type.c: New file.
	* stdio-common/reg-printf.c (__register_printf_specifier): New
	function.  Mostly the old __register_printf_function function but
	uses locking and type of third parameter changed.
	(__register_printf_function): Implement using
	__register_printf_specifier.
	* stdio-common/vfprintf.c (vfprintf): Collect argument sizes in
	calls to arginfo functions.  Allocate enough memory for user-defined
	types.  Call new va_arg functions to get user-defined types.
	Try installed handlers even for existing format specifiers first.