PR22047, Heap out of bounds read in parse_comp_unit

PR22047, Heap out of bounds read in parse_comp_unit

Like the PR22230 fix, we can allocate a buffer with an extra byte
rather than letting bfd_simple_get_relocated_section_contents malloc
and return a buffer.  Much better than allocating another buffer
afterwards.

	PR 22047
	* dwarf2.c (read_section): Allocate buffer with extra byte for
	bfd_simple_get_relocated_section_contents rather than copying
	afterwards.