test libdl before OpenSSL configuration

the bug has been introduced in r2818 and broke
*) SSL modules linking on Solaris 9 and lower,
*) and linking with OpenSSL built from sources on Linux

auto/os/features

@@ -230,3 +230,25 @@ ngx_feature_libs=
 ngx_feature_test="struct statvfs  fs;
                   statvfs(NULL, &fs);"
 . auto/feature
+
+
+ngx_feature="dlopen()"
+ngx_feature_name=
+ngx_feature_run=no
+ngx_feature_incs="#include <dlfcn.h>"
+ngx_feature_path=
+ngx_feature_libs=
+ngx_feature_test="dlopen(NULL, 0)"
+. auto/feature
+
+
+if [ $ngx_found != yes ]; then
+
+    ngx_feature="dlopen() in libdl"
+    ngx_feature_libs="-ldl"
+    . auto/feature
+
+    if [ $ngx_found = yes ]; then
+        NGX_LIBDL="-ldl"
+    fi
+fi

auto/unix

@@ -185,28 +185,6 @@ if [ $ngx_found != yes ]; then
 fi
 
 
-ngx_feature="dlopen()"
-ngx_feature_name=
-ngx_feature_run=no
-ngx_feature_incs="#include <dlfcn.h>"
-ngx_feature_path=
-ngx_feature_libs=
-ngx_feature_test="dlopen(NULL, 0)"
-. auto/feature
-
-
-if [ $ngx_found != yes ]; then
-
-    ngx_feature="dlopen() in libdl"
-    ngx_feature_libs="-ldl"
-    . auto/feature
-
-    if [ $ngx_found = yes ]; then
-        NGX_LIBDL="-ldl"
-    fi
-fi
-
-
 ngx_feature="mmap(MAP_ANON|MAP_SHARED)"
 ngx_feature_name="NGX_HAVE_MAP_ANON"
 ngx_feature_run=yes