c-family: clean up the data tables in c-format.c

c-family: clean up the data tables in c-format.c

The format_char_info tables in c-format.c for our own formats contain
a lot of repetition.

This patch adds a macro to express the conversion specifiers implemented
within pp_format, making it clearer which are custom ones added by the
various diagnostic_format_decoder callbacks.

Doing so uncovered a few mistakes in the data (based on comparison with
the source of the diagnostic_format_decoder callbacks, and the notes
below), which the patch fixes:

- gcc_diag_char_table didn't have 'Z', but it *is* implemented by pp_format.

- removed erroneous 'G' and 'K' entries from gcc_diag_char_table: they're
  implemented by default_tree_printer (and thus in "tdiag") and by the
  C/C++ FEs, but not in pp_format.

- removed "v" (lower case) from gcc_tdiag_char_table and
  gcc_cxxdiag_char_table

Notes:

pretty-print.h uses this for ATTRIBUTE_GCC_PPDIAG, used by pp_printf
and pp_verbatim:

whereas diagnostic-core.h uses this for ATTRIBUTE_GCC_DIAG, used by
the various diagnostic functions:

/* If we haven't already defined a front-end-specific diagnostics
   style, use the generic one.  */

Hence I'm assuming that __gcc_diag__ is for use for when we don't
know what kind of diagnostic_format_decoder we have, and we can
only rely on pp_format's core functionality, where __gcc_tdiag__
is allowed to assume default_tree_printer.

gcc/c-family/ChangeLog:
	* c-format.c (PP_FORMAT_CHAR_TABLE): New macro, based on existing
	table entries for gcc_diag_char_table, and the 'Z' entry from
	gcc_tdiag_char_table, changing the "chain" entry for 'Z' from
	&gcc_tdiag_char_table[0] to &gcc_diag_char_table[0].
	(gcc_diag_char_table): Use PP_FORMAT_CHAR_TABLE, implicitly
	adding missing "Z" for this table.  Remove erroneous "G" and "K"
	entries.
	(gcc_tdiag_char_table): Use PP_FORMAT_CHAR_TABLE.  Remove "v".
	(gcc_cdiag_char_table): Use PP_FORMAT_CHAR_TABLE.
	(gcc_cxxdiag_char_table): Use PP_FORMAT_CHAR_TABLE.  Remove "v".

gcc/testsuite/ChangeLog:
	* gcc.dg/format/gcc_diag-1.c (foo): Update the %v tests for
	tdiag and cxxdiag.
	* gcc.dg/format/gcc_diag-10.c (test_diag): Update tests of %G
	and %K.

From-SVN: r263181