Added "Implements" keyword.

blitz.mod/blitz.bmx

@@ -713,6 +713,11 @@ bbdoc: Specify user defined Type supertype
 keyword: "Extends"
 End Rem
 
+Rem
+bbdoc: Specify user defined Interface(s)
+keyword: "Implements"
+End Rem
+
 Rem
 bbdoc: Begin a Method declaration
 keyword: "Method"