Fix error: missing noexcept

GCC 8.2.0 -Wnoexcept flags two functions which should be marked as not throwing.

src/color.hpp

@@ -250,7 +250,7 @@ namespace std
 	template<>
 	struct hash<color_t>
 	{
-		size_t operator()(const color_t& c) const
+		size_t operator()(const color_t& c) const noexcept
 		{
 			return c.to_rgba_bytes();
 		}

src/map/location.hpp

@@ -210,7 +210,7 @@ std::ostream &operator<<(std::ostream &s, const std::vector<map_location>& v);
 namespace std {
 template<>
 struct hash<map_location> {
-	size_t operator()(const map_location& l) const {
+	size_t operator()(const map_location& l) const noexcept {
 		// The 2000 bias supposedly ensures that the correct x is recovered for negative y
 		// This implementation copied from the Lua location_set
 		return (l.wml_x()) * 16384 + (l.wml_y()) + 2000;