Issue #718: Fix TALOS-CAN-152

If a 7-Zip archive declares a rediculously large number of substreams,
it can overflow an internal counter, leading a subsequent memory
allocation to be too small for the substream data.

Thanks to the Open Source and Threat Intelligence project at Cisco
for reporting this issue.
archive_read_support_format_7zip_capabilities(struct archive_read * a)
{
	(void)a; /* UNUSED */
	return (ARCHIVE_READ_FORMAT_CAPS_ENCRYPT_DATA |
			ARCHIVE_READ_FORMAT_CAPS_ENCRYPT_METADATA);
}

archive_read_support_format_7zip_capabilities(struct archive_read * a)
{
	(void)a; /* UNUSED */
	return (ARCHIVE_READ_FORMAT_CAPS_ENCRYPT_DATA |
			ARCHIVE_READ_FORMAT_CAPS_ENCRYPT_METADATA);
}
