Configure: added -Wno-deprecated-declarations on OS X.

Previous workaround to avoid warnings on OS X due to deprecated system
OpenSSL library (introduced in a3870ea96ccd) no longer works, as
the MAC_OS_X_VERSION_MIN_REQUIRED macro is ignored on OS X 10.9
if a compiler used supports __attribute__(availability).
diff --git a/auto/cc/clang b/auto/cc/clang
index baaf4ba..25707b4 100644
--- a/auto/cc/clang
+++ b/auto/cc/clang
@@ -88,6 +88,11 @@
 # we have a lot of unused function arguments
 CFLAGS="$CFLAGS -Wno-unused-parameter"
 
+# deprecated system OpenSSL library on OS X
+if [ "$NGX_SYSTEM" = "Darwin" ]; then
+    CFLAGS="$CFLAGS -Wno-deprecated-declarations"
+fi
+
 # stop on warning
 CFLAGS="$CFLAGS -Werror"
 
diff --git a/auto/cc/gcc b/auto/cc/gcc
index c27d857..727f11e 100644
--- a/auto/cc/gcc
+++ b/auto/cc/gcc
@@ -158,6 +158,11 @@
         CFLAGS="$CFLAGS -Wno-unused-parameter"
         # 4.2.1 shows the warning in wrong places
         #CFLAGS="$CFLAGS -Wunreachable-code"
+
+        # deprecated system OpenSSL library on OS X
+        if [ "$NGX_SYSTEM" = "Darwin" ]; then
+            CFLAGS="$CFLAGS -Wno-deprecated-declarations"
+        fi
     ;;
 
     *)
diff --git a/src/os/unix/ngx_darwin_config.h b/src/os/unix/ngx_darwin_config.h
index 7ac86c7..bbad977 100644
--- a/src/os/unix/ngx_darwin_config.h
+++ b/src/os/unix/ngx_darwin_config.h
@@ -9,9 +9,6 @@
 #define _NGX_DARWIN_CONFIG_H_INCLUDED_
 
 
-#define MAC_OS_X_VERSION_MIN_REQUIRED MAC_OS_X_VERSION_10_0
-
-
 #include <sys/types.h>
 #include <sys/time.h>
 #include <unistd.h>