Add a server scope for Lua states (in LuaScope), which creates a pool of ...

Add a server scope for Lua states (in LuaScope), which creates a pool of  states with manageable minimum and maximum size.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1369656 13f79535-47bb-0310-9956-ffa450edef68