Improve Lua 5.2.0 compatibility.

This is not yet complete. Building should
still work with Lua 5.1.4, but needs
-DLUA_COMPAT_ALL in CPPFLAGS when compiled
against 5.2.0. Automatically handling
this in configure is still a TODO.

Backport from trunk of the following revisions:

r1221205: Make mod_lua compile with lua 5.2.x.
MOdified patch submitted by NormW (nornw gknw net).

r1239029: luaL_reg was already deprecated in Lua 5.1.4.
It is gone in Lua 5.2.0 and was replaced by luaL_Reg
which already existed in 5.1.4. So use that one.

r1239030: Remove luaL_reg macro definition no longer needed
and simplify lua_load compatibility macro.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1239120 13f79535-47bb-0310-9956-ffa450edef68