Fixes the X86 Base template.

It turns out that using using TargetLowering::<member> causes problems when compiling with g++. The problem was fixed by using
Machine:: instead, where Machine is the template parameter. With name-dependent identifier, g++ does the right thing.

BUG= None
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/1208663002.
diff --git a/src/IceCfg.h b/src/IceCfg.h
index e96804c..83c4ddd 100644
--- a/src/IceCfg.h
+++ b/src/IceCfg.h
@@ -104,6 +104,8 @@
   // Manage Variables.
   // Create a new Variable with a particular type and an optional
   // name.  The Node argument is the node where the variable is defined.
+  // TODO(jpp): untemplate this with two separate methods: makeVariable and
+  // makeSpillVariable.
   template <typename T = Variable> T *makeVariable(Type Ty) {
     SizeT Index = Variables.size();
     T *Var = T::create(this, Ty, Index);