berkeley-db4: fix build under Xcode 4.6

Formula/berkeley-db4.rb

@@ -7,6 +7,9 @@ class BerkeleyDb4 < Formula
 
   keg_only "BDB 4.8.30 is provided for software that doesn't compile against newer versions."
 
+  # Fix build under Xcode 4.6
+  def patches; DATA; end
+
   def install
     # BerkeleyDB dislikes parallel builds
     ENV.deparallelize
@@ -27,3 +30,27 @@ class BerkeleyDb4 < Formula
     end
   end
 end
+
+__END__
+diff --git a/dbinc/atomic.h b/dbinc/atomic.h
+index 0034dcc..50b8b74 100644
+--- a/dbinc/atomic.h
++++ b/dbinc/atomic.h
+@@ -144,7 +144,7 @@ typedef LONG volatile *interlocked_val;
+ #define	atomic_inc(env, p)	__atomic_inc(p)
+ #define	atomic_dec(env, p)	__atomic_dec(p)
+ #define	atomic_compare_exchange(env, p, o, n)	\
+-	__atomic_compare_exchange((p), (o), (n))
++	__atomic_compare_exchange_db((p), (o), (n))
+ static inline int __atomic_inc(db_atomic_t *p)
+ {
+ 	int	temp;
+@@ -176,7 +176,7 @@ static inline int __atomic_dec(db_atomic_t *p)
+  * http://gcc.gnu.org/onlinedocs/gcc-4.1.0/gcc/Atomic-Builtins.html
+  * which configure could be changed to use.
+  */
+-static inline int __atomic_compare_exchange(
++static inline int __atomic_compare_exchange_db(
+ 	db_atomic_t *p, atomic_value_t oldval, atomic_value_t newval)
+ {
+ 	atomic_value_t was;