Make love compile against lua5.2

src/common/runtime.cpp

@@ -486,6 +486,13 @@ int luax_getregistry(lua_State *L, Registry r)
 	}
 }
 
+extern "C" int luax_typerror(lua_State *L, int narg, const char *tname)
+{
+	const char *msg = lua_pushfstring(L, "%s expected, got %s",
+	                                  tname, luaL_typename(L, narg));
+	return luaL_argerror(L, narg, msg);
+}
+
 StringMap<Type, TYPE_MAX_ENUM>::Entry typeEntries[] =
 {
 	{"Invalid", INVALID_ID},

src/common/runtime.h

@@ -26,6 +26,7 @@
 
 // Lua
 extern "C" {
+	#define LUA_COMPAT_ALL
 	#include <lua.h>
 	#include <lualib.h>
 	#include <lauxlib.h>
@@ -346,6 +347,10 @@ int luax_insistlove(lua_State *L, const char *k);
  **/
 int luax_getregistry(lua_State *L, Registry r);
 
+extern "C" { // Also called from luasocket
+	int luax_typerror(lua_State *L, int narg, const char *tname);
+}
+
 /**
  * Like luax_totype, but causes an error if the value at idx is not Proxy,
  * or is not the specified type.