c: Add Walloc-size to warn about insufficient size in allocations [PR71219]

c: Add Walloc-size to warn about insufficient size in allocations [PR71219]

Add option Walloc-size that warns about allocations that have
insufficient storage for the target type of the pointer the
storage is assigned to. Added to Wextra.

	PR c/71219
gcc:
	* doc/invoke.texi: Document -Walloc-size option.

gcc/c-family:

	* c.opt (Walloc-size): New option.

gcc/c:
	* c-typeck.cc (convert_for_assignment): Add warning.

gcc/testsuite:

	* gcc.dg/Walloc-size-1.c: New test.
	* gcc.dg/Walloc-size-2.c: New test.