change build names a little and document

lib/risc/method_compiler.rb

@@ -79,7 +79,7 @@ module Risc
         instruction = instruction.next
       end
     end
-    
+
     # add a risc instruction after the current (insertion point)
     # the added instruction will become the new insertion point
     def add_code( instruction )
@@ -170,5 +170,15 @@ module Risc
     def reduce_int( source , register )
       add_slot_to_reg( source + "int -> fix" , register , Parfait::Integer.integer_index , register)
     end
+
+    # Build with builder (see there), adding the created instructions
+    def build(&block)
+      builder.build_and_return(&block)
+    end
+
+    # return a new builder that uses this compiler
+    def builder
+      Builder.new(self)
+    end
   end
 end