move type resolution to compiler

from risc_value.
also unite mock compilers

test/support/fake_compiler.rb

@@ -0,0 +1,17 @@
+module Risc
+  class FakeCompiler
+    def slot_type(slot,type)
+      type.type_for(slot)
+    end
+    def resolve_type(name)
+      Parfait.object_space.types.values.first
+    end
+    def use_reg(type)
+      RegisterValue.new(:r1 , type)
+    end
+    def reset_regs
+    end
+    def add_constant(c)
+    end
+  end
+end