pass extra info into register init, not just value

extra info may be hash, maybe just type info

lib/risc/callable_compiler.rb

@@ -53,12 +53,13 @@ module Risc
     end
 
     # require a (temporary) register. code must give this back with release_reg
-    def use_reg( type , value = nil )
+    # Second extra parameter may give extra info about the value, see RegisterValue
+    def use_reg( type , extra = {} )
       raise "Not type #{type.inspect}" unless type.is_a?(Symbol) or type.is_a?(Parfait::Type)
       if @regs.empty?
-        reg = Risc.tmp_reg(type , value)
+        reg = Risc.tmp_reg(type , extra)
       else
-        reg = @regs.last.next_reg_use(type , value)
+        reg = @regs.last.next_reg_use(type , extra)
       end
       @regs << reg
       return reg