extend meta_enum: add a members_of<Enum>() function to get a range over all declared values
For enums declared with the meta_enum
macro, e.g
meta_enum_class( MyEnum,int, Unknown = 0, Case1, Case2, Case1000 = 1000 )
it is now possible to write a loop over all declared values, e.g.
for (MyEnum i : members_of<MyEnum>() ) ...