* intl.h (open_quote, close_quote): New.
* intl.c (open_quote, close_quote): New.
(gcc_init_libintl): Set them.
* pretty-print.c: Include "intl.h".
(pp_base_format_text): Support 'q' format flag and %` and %'
formats. Use ' instead of ` in comments.
* c-format.c (gcc_diag_flag_specs, gcc_cxxdiag_flag_specs,
gcc_diag_char_table, gcc_cdiag_char_table, gcc_cxxdiag_char_table,
foramt_types_orig): Describe these new formats.
(decode_format_attr, check_function_format,
check_format_info_main): Use these new formats.
(status_warning): Use ATTRIBUTE_GCC_DIAG.
* toplev.c (ATTRIBUTE_GCC_DIAG): Increase required GCC version to
check these formats to 3.5.