vec: Silence clang warning

I noticed during compatibility testing that clang warns that this
operator won't be implicitly const in C++14 onwards.

gcc/
	* vec.h (vnull::operator vec<T, A, L>): Make const.

1 files changed, 1 insertions, 1 deletions

diff --git a/gcc/vec.h b/gcc/vec.h
index 09166f1..31574b4 100644
--- a/gcc/vec.h
+++ b/gcc/vec.h
@@ -550,7 +550,7 @@ vec_copy_construct (T *dst, const T *src, unsigned n)
 struct vnull
 {
   template <typename T, typename A, typename L>
-  CONSTEXPR operator vec<T, A, L> () { return vec<T, A, L>(); }
+  CONSTEXPR operator vec<T, A, L> () const { return vec<T, A, L>(); }
 };
 extern vnull vNULL;