c: Turn int-conversion warnings into permerrors

gcc/

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

gcc/c/

	PR c/96284
	PR c/106416
	* c-typeck.cc (build_conditional_expr): Use permerror_opt for
	pointer/integer type mismatches, based on -Wint-conversion.
	(pedwarn_permerror_init, permerror_init): New function.
	(pedwarn_init): Call pedwarn_permerror_init.
	(convert_for_assignment): Use permerror_opt and
	permerror_init for -Wint-conversion warnings.

gcc/testsuite/

	* gcc.dg/permerror-default.c (int_conversion_1)
	(int_conversion_2): Expect the new permerrors.
	* gcc.dg/permerror-gnu89-nopermissive.c (int_conversion_1)
	(int_conversion_2): Likewise.
	* gcc.dg/permerror-system.c: Likewise.
	* c-c++-common/pr77624-1.c (foo, bar): Expect
	error instead of warning.
	* gcc.dg/Wint-conversion-2.c: Compile with -fpermissive due
	to expected int-conversion warning.
	* gcc.dg/Wint-conversion-3.c: Likewise.
	* gcc.dg/Wint-conversion-4.c: New test.  Based on
	gcc.dg/Wint-conversion-3.c.  Expect int-conversion errors.
	* gcc.dg/assign-warn-1.c: Compile with -fpermissive.
	* gcc.dg/assign-warn-4.c: New file.  Extracted from
	assign-warn1.c.  Expect int-conversion errors.
	* gcc.dg/diagnostic-types-1.c: Compile with -fpermissive.
	* gcc.dg/diagnostic-types-2.c: New file.  Extracted from
	gcc.dg/diagnostic-types-1.c.  Expect some errors instead of
	warnings.
	* gcc.dg/gomp/pr35738.c: Compile with -fpermissive due to
	expected int-conversion error.
	* gcc.dg/gomp/pr35738-2.c: New test.  Based on
	gcc.dg/gomp/pr35738.c.  Expect int-converison errors.
	* gcc.dg/init-excess-3.c: Expect int-converison errors.
	* gcc.dg/overflow-warn-1.c: Likewise.
	* gcc.dg/overflow-warn-3.c: Likewise.
	* gcc.dg/param-type-mismatch.c: Compile with -fpermissive.
	* gcc.dg/param-type-mismatch-2.c: New test.  Copied from
	gcc.dg/param-type-mismatch.c.  Expect errors.
	* gcc.dg/pr61162-2.c: Compile with -fpermissive.
	* gcc.dg/pr61162-3.c: New test. Extracted from
	gcc.dg/pr61162-2.c.  Expect int-conversion errors.
	* gcc.dg/spec-barrier-3.c: Use -fpermissive due to expected
	int-conversion error.
	* gcc.dg/spec-barrier-3a.c: New test.  Based on
	gcc.dg/spec-barrier-3.c.  Expect int-conversion errors.
	* gcc.target/aarch64/acle/memtag_2.c: Use -fpermissive due to expected
	int-conversion error.
	* gcc.target/aarch64/acle/memtag_2a.c: New test.  Copied from
	gcc.target/aarch64/acle/memtag_2.c.  Expect error.
	* gcc.target/aarch64/sve/acle/general-c/load_3.c (f1): Expect
	error.
	* 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.