Allow LuaJIT to be used

[victorhora]

Following the addition of Lua 5.1 compatibility with libModSecurity at dee9898, this PR tries to address support for LuaJIT. The output of the configure script after applying the patch should be something like:

...
configure: LUA library found at: /usr/lib/x86_64-linux-gnu//libluajit-5.1.so
configure: LUA headers found at: /usr/include/luajit-2.0
configure: LUA version from includes: 501
configure: using LUA -lluajit-5.1
...

   + LUA                                           ....found v501
      -lluajit-5.1 -L/usr/lib/x86_64-linux-gnu/, -DWITH_LUA -DWITH_LUA_5_1 -I/usr/include/luajit-2.0

Should finish solving the issue regarding LuaJIT support at #1809

[theMiddleBlue]

It works like a charm!

thanks a lot @victorhora and @p0pr0ck5 !

[victorhora]

Merged as of 857bf9d

Thanks for the feedback @theMiddleBlue ;)