Add socks 4a proxy support

[adfoster-r7]

Requested from #69

Let's update rex-socket to support socks4a; current the DNS resolution happens locally - and doesn't support the ability to perform DNS resolution remotely via the socks proxy:

rex-socket/lib/rex/socket/comm/local.rb

Lines 448 to 451 in e6c2e61

	when 'socks4'
	supports_ipv6 = false
	setup = [4,1,port.to_i].pack('CCn') + Rex::Socket.resolv_nbo(host, supports_ipv6) + Rex::Text.rand_text_alpha(rand(8)+1) + "\x00"
	size = sock.put(setup)