Add experimental Lua support to Ettercap

- Enabled via ENABLE_LUA=On
- Depends upon LuaJIT
- Will use bundled LuaJIT if system doesn't provide.
- Leveraged via --lua-script command line.
- Currently, Lua scripts can hook to any hook point. Will eventually
  move toward drop-in replacements for C-based protocol dissectors.
Initial import  of lua basics, more to come
fixing omitted files
Adding in string additions
final mods to scripts to bring them up to speed
Added SRV query handling to DNS spoof
Sync ettercap_ffi w/ recent ec_packet.h change
Merge branch 'add_experimental_lua_support' into lua_staging
Added packet metamethods.
Added third-party lua stdlib library.
Changed --lua-script FILENAME load behavior

- First, it checks to see if it can load FILENAME directly. This can be
  a relative path from the current working directory, or a full path to
  a file.

- If that fails, then it will 'share/lua/scripts/' install directory for
  FILENAME. You are now expected to provide the file extension
  (previously, it would auto-append '.lua')
Better error handling for lua script loading

- Fatal error if the lua script doesn't parse properly.

- Script load errors now exit using ettercap standard methods
Added more flag handling, stopped set_data overflow
Ensure that has_data returns a boolean
Added l4_summary
Remove a crummy script, add a neat script.

- Removed half-done smb_creds.lua

- Add neato example smtp_redir.lua
Merge branch 'mdns-fixes' into dns-spoof-updates
Added checks to strtok
Merge pull request #156 from justfalter/add_experimental_lua_support

Add experimental Lua support to Ettercap
Merge pull request #186 from eaescob/dns-spoof-updates

Dns spoof updates