Add Enum constraint to enummap

Fix typo in enumset require

lib/std/collections/enummap.c3

@@ -1,3 +1,6 @@
+/**
+ * @require Enum.kindof == TypeKind.ENUM : "Only enums may be used with an enummap"
+ **/
 module std::collections::enummap(<Enum, ValueType>);
 import std::io;
 struct EnumMap (Printable)

lib/std/collections/enumset.c3

@@ -3,7 +3,7 @@
 // a copy of which can be found in the LICENSE_STDLIB file.
 
 /**
- * @require Enum.kindof == TypeKind.ENUM : "Only enums maybe be used with an enumset"
+ * @require Enum.kindof == TypeKind.ENUM : "Only enums may be used with an enumset"
  **/
 module std::collections::enumset(<Enum>);
 import std::io;