Lua 5.2 and cmake

Hi leo,

I had two problems with Lua/cmake:

 1. I had Lua 5.1.5, but FinaLua52.cmake recognized it as 5.2 and led a build failure (because ``luaL_setfuncs`` only exists in 5.2+)
 2. When there is no Lua installed, we had a build failure at ``src/shell/lua/leanlua.cpp`` since ``iostream`` is not included.

I fixed them in this pull request and tested them on OSX and Ubuntu 12.04. Please take a look at the changes. Thank you.

Soonho