Guard the noexcept with __cplusplus version.

[logan]

Summary

To allow the compilation with gcc, we can't use the
has_feature(noexcept) to detect the existence of noexcept
keyword. We should use cplusplus >= 201103L instead.

[logan]

Committed as rL208465.

test/test_vector1.cpp

 
 int gConstructorCounter;
 int gConstructorThrowTarget;
 int gDestructorCounter;
 int gDestructorThrowTarget;
 void throw_construct ( void *p ) { if ( gConstructorCounter   == gConstructorThrowTarget ) throw 1; ++gConstructorCounter; }
 void throw_destruct  ( void *p ) { if ( ++gDestructorCounter  == gDestructorThrowTarget  ) throw 2; }
 
-#if __has_feature(cxx_noexcept)
+#if __cplusplus >= 201103L
 #   define CAN_THROW noexcept(false)
 #else
 #   define CAN_THROW
 #endif
 
 struct vec_on_stack {
     void *storage;
     vec_on_stack () : storage ( __cxxabiv1::__cxa_vec_new    (            10, 40, 8, throw_construct, throw_destruct )) {}