c: Turn -Wincompatible-pointer-types into a permerror

The change to build_conditional_expr drops the downgrade
from a pedwarn to warning for builtins for C99 and later
language dialects.  It remains a warning in C89 mode (not
a permerror), as the -std=gnu89 -fno-permissive test shows.

gcc/

	* doc/invoke.texi (Warning Options): Document changes.

gcc/c/

	PR c/96284
	* c-typeck.cc (build_conditional_expr): Upgrade most pointer
	type mismatches to a permerror.
	(convert_for_assignment): Use permerror_opt and
	permerror_init for OPT_Wincompatible_pointer_types warnings.

gcc/testsuite/

	* gcc.dg/permerror-default.c (incompatible_pointer_types):
	Expect new permerror.
	* gcc.dg/permerror-gnu89-nopermissive.c
	(incompatible_pointer_types): Likewise.
	* gcc.dg/permerror-pedantic.c (incompatible_pointer_types):
	Likewise.
	* gcc.dg/permerror-system.c: Likewise.
	* gcc.dg/Wincompatible-pointer-types-2.c: Compile with
	-fpermissive due to expected errors.
	* gcc.dg/Wincompatible-pointer-types-5.c: New test.  Copied
	from gcc.dg/Wincompatible-pointer-types-2.c.  Expect errors.
	* gcc.dg/anon-struct-11.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/anon-struct-11a.c: New test.  Copied from
	gcc.dg/anon-struct-11.c.  Expect errors.
	* gcc.dg/anon-struct-13.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/anon-struct-13a.c: New test.  Copied from
	gcc.dg/anon-struct-13.c.  Expect errors.
	* gcc.dg/builtin-arith-overflow-4.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/builtin-arith-overflow-4a.c: New test.  Copied from
	gcc.dg/builtin-arith-overflow-4.c.  Expect errors.
	* gcc.dg/c23-qual-4.c: Expect -Wincompatible-pointer-types errors.
	* gcc.dg/dfp/composite-type.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/dfp/composite-type-2.c: New test.  Copied from
	gcc.dg/dfp/composite-type.c.  Expect errors.
	* gcc.dg/diag-aka-1.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/diag-aka-1a.c: New test.  Copied from
	gcc.dg/diag-aka-1a.c.  Expect errors.
	* gcc.dg/enum-compat-1.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/enum-compat-2.c: New test.  Copied from
	gcc.dg/enum-compat-1.c.  Expect errors.
	* gcc.dg/func-ptr-conv-1.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/func-ptr-conv-2.c: New test.  Copied from
	gcc.dg/func-ptr-conv-1.c.  Expect errors.
	* gcc.dg/init-bad-7.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/init-bad-7a.c: New test.  Copied from gcc.dg/init-bad-7.c.
	Expect errors.
	* gcc.dg/noncompile/incomplete-3.c (foo): Expect
	-Wincompatible-pointer-types error.
	* gcc.dg/param-type-mismatch-2.c (test8): Likewise.
	* gcc.dg/pointer-array-atomic.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/pointer-array-atomic-2.c: New test.  Copied from
	gcc.dg/pointer-array-atomic.c.  Expect errors.
	* gcc.dg/pointer-array-quals-1.c (test): Expect
	-Wincompatible-pointer-types errors.
	* gcc.dg/transparent-union-1.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/transparent-union-1a.c: New test.  Copied from
	gcc.dg/transparent-union-1.c.  Expect errors.
	* gcc.target/aarch64/acle/memtag_2a.c
	(test_memtag_warning_return_qualifier): Expect additional
	errors.
	* gcc.target/aarch64/sve/acle/general-c/load_2.c (f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_1.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_2.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_3.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_4.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_5.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_restricted_1.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_restricted_2.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_restricted_3.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_restricted_4.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/sizeless-1.c (f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/sizeless-2.c (f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/store_1.c (f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/store_2.c (f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/store_scatter_index_1.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/store_scatter_index_restricted_1.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/store_scatter_offset_2.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/store_scatter_offset_restricted_1.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general/attributes_7.c
	(f1): Likewise.
	* gcc.target/i386/sse2-bfloat16-scalar-typecheck.c (footest):
	Expect -Wincompatible-pointer-types errors.
	* gcc.target/i386/vect-bfloat16-typecheck_1.c (footest): Likewise.
	* gcc.target/i386/vect-bfloat16-typecheck_2.c (footest): Likewise.