resolve #47 [rt.cpan.org #15065] - -set-cookie...

behaviour made consistent with that of -cookie, previously passing
an ARRAY ref to -set-cookie would not work, witness:

	$cgi->header('-cookie'=>'x=y')
	# Set-cookie: x=y

	$cgi->header('-set-cookie'=>'x=y')
	# Set-cookie: x=y

	$cgi->header('-cookie'=>['x=y','a=b'])
	# Set-Cookie: x=y
	# Set-Cookie: a=b

	$cgi->header('-set-cookie'=>['x=y','a=b'])
	# Set-cookie: ARRAY(0x816607c)

now the behaviour of the latter is fixed to accept an ARRAY ref.

thanks to JWILLIAMS@cpan.org for the patch and test cases