Major recode of --os-pwn functionality. Now the Metasploit shellcode can not be run as a Metasploit generated payload stager anymore. Instead it can be run on the target system either via sys_bineval() (as it was before, anti-forensics mode, all the same) or via shellcodeexec executable. Advantages are that:

* It is stealthier as the shellcode itself does not touch the filesystem, it's an argument passed to shellcodeexec at runtime.
* shellcodeexec is not (yet) recognized as malicious by any (Avast excluded) AV product.
* shellcodeexec binary size is significantly smaller than a Metasploit payload stager (even when packed with UPX).
* UPX now is not needed anymore, so sqlmap package is also way smaller and less likely to be detected itself as malicious by your AV software.
shellcodeexec source code, compilation files and binaries are in extra/shellcodeexec/ folder now - copied over from https://github.com/inquisb/shellcodeexec.
Minor code refactoring.