an internal MD5 implemenation
patch by Maxim Dounin
diff --git a/auto/lib/conf b/auto/lib/conf
index 60e891b..f89d922 100644
--- a/auto/lib/conf
+++ b/auto/lib/conf
@@ -29,6 +29,7 @@
     if [ $USE_OPENSSL = YES ]; then
         have=NGX_HAVE_OPENSSL_MD5_H . auto/have
         have=NGX_OPENSSL_MD5 . auto/have
+        have=NGX_HAVE_MD5 . auto/have
         MD5=YES
         MD5_LIB=OpenSSL