2013-04-19  Evgeniy Stepanov <eugenis@google.com>

	* src/c++11/system_error.cc: Add explicit default constructors.
	* src/c++11/future.cc: Likewise.

Index: src/c++11/system_error.cc
===================================================================
--- src/c++11/system_error.cc	(revision 198023)
+++ src/c++11/system_error.cc	(working copy)
@@ -34,6 +34,7 @@
   
   struct generic_error_category : public std::error_category
   {
+    generic_error_category() {}
     virtual const char*
     name() const noexcept
     { return "generic"; }
@@ -49,6 +50,7 @@
 
   struct system_error_category : public std::error_category
   {
+    system_error_category() {}
     virtual const char*
     name() const noexcept
     { return "system"; }
Index: src/c++11/future.cc
===================================================================
--- src/c++11/future.cc	(revision 198023)
+++ src/c++11/future.cc	(working copy)
@@ -28,6 +28,7 @@
 {
   struct future_error_category : public std::error_category
   {
+    future_error_category() {}
     virtual const char*
     name() const noexcept
     { return "future"; }