Add support for invoke-static in optimizing compiler.

Support is limited to calls without parameters and returning
void. For simplicity, we currently follow the Quick ABI.

Change-Id: I54805161141b7eac5959f1cae0dc138dd0b2e8a5
diff --git a/compiler/utils/x86/assembler_x86.h b/compiler/utils/x86/assembler_x86.h
index e284d8c..67356af 100644
--- a/compiler/utils/x86/assembler_x86.h
+++ b/compiler/utils/x86/assembler_x86.h
@@ -227,6 +227,7 @@
   void call(Register reg);
   void call(const Address& address);
   void call(Label* label);
+  void call(const ExternalLabel& label);
 
   void pushl(Register reg);
   void pushl(const Address& address);