* locale/xlocale.c (_nl_C_locobj): Mark as const.

	* include/locale.h: Define _nl_C_locobj_ptr.
	* iconv/gconv_charset.h: Use _nl_C_locobj_ptr instead of using pointer
	to _nl_C_locobj because we also need a cast.
	* iconv/gconv_conf.c: Likewise.
	* iconv/gconv_int.h: Likewise.
	* iconv/gconv_open.c: Likewise.
	* locale/duplocale.c: Likewise.
	* locale/freelocale.c: Likewise.
	* locale/newlocale.c: Likewise.
	* misc/syslog.c: Likewise.
	* stdlib/strtod_l.c: Likewise.
	* sysdeps/unix/sysv/linux/getloadavg.c: Likewise.