Rename __atomic_compare_exchange to not clash with gcc built-in

Downloaded from
https://src.fedoraproject.org/cgit/rpms/libdb.git/commit/?id=d6841b3b46a51db98c162347211a5a64d154ea37

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>

--- db-5.3.28/src/dbinc/atomic.h.old	2018-05-23 09:20:04.216914922 +0200
+++ db-5.3.28/src/dbinc/atomic.h	2018-05-23 09:20:49.510057897 +0200
@@ -144,7 +144,7 @@
 #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))
+	__db_atomic_compare_exchange((p), (o), (n))
 static inline int __atomic_inc(db_atomic_t *p)
 {
 	int	temp;
@@ -176,7 +176,7 @@
  * 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 __db_atomic_compare_exchange(
 	db_atomic_t *p, atomic_value_t oldval, atomic_value_t newval)
 {
 	atomic_value_t was;