Include charset.h.

Include charset.h.
(Vprint_charset_text_property): New variable.
(Qdefault): Extern it.
(PRINT_STRING_NON_CHARSET_FOUND)
(PRINT_STRING_UNSAFE_CHARSET_FOUND): New macros.
(print_check_string_result): New variable.
(print_check_string_charset_prop): New function.
(print_prune_charset_plist): New variable.
(print_prune_string_charset): New function.
(print_object): Call print_prune_string_charset if
Vprint_charset_text_property is not t.
(print_interval): Print nothing if itnerval->plist is nil.
(syms_of_print): Declare Vprint_charset_text_property as a lisp
variable.  Init and staticpro print_prune_charset_plist.