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
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 pull request #156 from justfalter/add_experimental_lua_support

Add experimental Lua support to Ettercap