Prevent attempts to call strncpy with a zero-length field by chacking the size of...

Prevent attempts to call strncpy with a zero-length field by chacking the size of debuglink sections.

	PR 22794
	* opncls.c (bfd_get_debug_link_info_1): Check the size of the
	section before attempting to read it in.
	(bfd_get_alt_debug_link_info): Likewise.