Silence class vs. struct warnings (vec)

[Oleg Endo]

Hi,

When building GCC on OSX with its native XCode/Clang tools, it outputs
quite some "struct X was previously declared as a class" or similar
warnings (-Wmismatched-tags is enabled by default).

The attached patch fixes a mismatch in struct vec_prefix when referring
to struct vec.

Tested with make all-gcc.
OK for trunk?

Cheers,
Oleg

gcc/ChangeLog:
        * vec.h (struct vec_prefix): Use struct vec instead of class 
        vec.

Index: gcc/vec.h
===================================================================
--- gcc/vec.h	(revision 205573)
+++ gcc/vec.h	(working copy)
@@ -1216,7 +1216,7 @@
   }
 
 private:
-  friend class vec<T, va_heap, vl_ptr>;
+  friend struct vec<T, va_heap, vl_ptr>;
 
   vec_prefix m_header;
   T m_data[N];