std::map can no longer be iterated over with pairs

[nimble0]

Example:

#define SOL_ALL_SAFETIES_ON 1
#include <sol/sol.hpp>

#include <iostream>
#include <map>

int main(int, char**) {
	sol::state lua;
	lua.open_libraries();

	std::map<int, std::string> myMap
	{
		{3, "three"},
		{10, "ten"},
		{5, "five"},
	};

	std::cout << "cpp iteration:" << std::endl;
	for(auto& kv : myMap)
		std::cout << kv.first << ": " << kv.second << "\n";
	std::cout << std::endl;

	lua["myMap"] = myMap;
	lua["myMap2"] = sol::as_table(myMap);

	lua.script(R"(

print("lua myMap iteration:")
for k, v in pairs(myMap) do
	print(k, ":", v)
end
print()

print("lua sol::as_table(myMap) iteration:")
for k, v in pairs(myMap2) do
	print(k, ":", v)
end
print()

	)");

	return 0;
}

Output:

cpp iteration:
3: three
5: five
10: ten

lua myMap iteration:

lua sol::as_table(myMap) iteration:
3	:	three
10	:	ten
5	:	five

This was introduced in 64e3823.