Merge pull request #5788 from ab9rf/enum_field_flexicast

improve `enum_field` with more flexible casting

Author: ab9rf

docs/changelog.txt

@@ -65,6 +65,7 @@ Template for new versions:
 ## Documentation
 
 ## API
+- add flexible casting to ``enum_field`` to enable explicit casting to more types
 
 ## Lua
 

library/include/DataDefs.h

@@ -632,6 +632,10 @@ namespace df
         enum_field<EnumType,IntType> &operator=(EnumType ev) {
             value = IntType(ev); return *this;
         }
+        explicit operator IntType () const { return IntType(value); }
+        template <typename T>
+        explicit operator T () const { return static_cast<T>(IntType(value)); }
+
     };
 
     template<class ET, class IT>