Support building ngx_pagespeed as a dynamic module.

As of 1.9.11, nginx supports loading dynamic modules
This change makes us support building ngx_pagespeed.so

Fixes https://github.com/pagespeed/ngx_pagespeed/issues/1116

config

@@ -193,7 +193,14 @@ ngx_feature_test="
 # Test whether we have pagespeed and can compile and link against it.
 . "$ngx_addon_dir/cpp_feature"
 
-if [ $ngx_found = yes ]; then
+if [ $ngx_found = no ]; then
+  cat << END
+$0: error: module ngx_pagespeed requires the pagespeed optimization library.
+Look in obj/autoconf.err for more details.
+END
+  exit 1
+fi
+
 ps_src="$ngx_addon_dir/src"
 ngx_addon_name=ngx_pagespeed
 NGX_ADDON_DEPS="$NGX_ADDON_DEPS \
@@ -211,7 +218,7 @@ if [ $ngx_found = yes ]; then
 $ps_src/ngx_server_context.h \
 $ps_src/ngx_url_async_fetcher.h \
 $psol_binary"
-  NGX_ADDON_SRCS="$NGX_ADDON_SRCS \
+NPS_SRCS=" \
 $ps_src/log_message_handler.cc \
 $ps_src/ngx_base_fetch.cc \
 $ps_src/ngx_caching_headers.cc \
@@ -226,39 +233,83 @@ if [ $ngx_found = yes ]; then
 $ps_src/ngx_server_context.cc \
 $ps_src/ngx_url_async_fetcher.cc"
 # Save our sources in a separate var since we may need it in config.make
-  PS_NGX_SRCS="$NGX_ADDON_SRCS"
+PS_NGX_SRCS="$NGX_ADDON_SRCS \
+$NPS_SRCS"
 
+# Make pagespeed run immediately before gzip and Brotli.
+if echo $HTTP_FILTER_MODULES | grep ngx_http_brotli_filter_module >/dev/null; then
+  next=ngx_http_brotli_filter_module
+elif [ $HTTP_GZIP = YES ]; then
+  next=ngx_http_gzip_filter_module
+else
+  next=ngx_http_range_header_filter_module
+fi
+
+if [ -n "$ngx_module_link" ]; then
+  # nginx-1.9.11+
+  ngx_module_type=HTTP_FILTER
+  ngx_module_name="ngx_pagespeed ngx_pagespeed_etag_filter"
+  ngx_module_incs="$ngx_feature_path"
+  ngx_module_deps=
+  ngx_module_srcs="$NPS_SRCS"
+  ngx_module_libs="$ngx_feature_libs"
+  ngx_module_order="ngx_http_range_header_filter_module\
+                    ngx_pagespeed_etag_filter\
+                    ngx_http_gzip_filter_module \
+                    ngx_http_brotli_filter_module \
+                    ngx_pagespeed \
+                    ngx_http_postpone_filter_module \
+                    ngx_http_ssi_filter_module \
+                    ngx_http_charset_filter_module \
+                    ngx_http_xslt_filter_module \
+                    ngx_http_image_filter_module \
+                    ngx_http_sub_filter_module \
+                    ngx_http_addition_filter_module \
+                    ngx_http_gunzip_filter_module \
+                    ngx_http_userid_filter_module \
+                    ngx_http_headers_filter_module"
+
+    . auto/module
+
+    if [ $ngx_module_link != DYNAMIC ]; then
+      # ngx_module_order doesn't work with static modules,
+      # so we must re-order filters here.
       if [ "$position_aux" = "true" ] ; then
         HTTP_AUX_FILTER_MODULES="$HTTP_AUX_FILTER_MODULES $ngx_addon_name"
       else
-    # Make pagespeed run immediately before gzip and Brotli.
-    if echo $HTTP_FILTER_MODULES | grep ngx_http_brotli_filter_module >/dev/null; then
-      module=ngx_http_brotli_filter_module
-    elif [ $HTTP_GZIP = YES ]; then
-      module=ngx_http_gzip_filter_module
-    else
-      module=ngx_http_range_header_filter_module
+        HTTP_FILTER_MODULES=$(echo $HTTP_FILTER_MODULES \
+                             | sed "s/ngx_pagespeed//" \
+                             | sed "s/$next/$next ngx_pagespeed/")
       fi
-
-    HTTP_FILTER_MODULES=$(echo $HTTP_FILTER_MODULES |\
-      sed "s/$module/$module $ngx_addon_name/")
+      # Make the etag header filter run immediately before range header filter.
+      HTTP_FILTER_MODULES=$(echo $HTTP_FILTER_MODULES \
+                           | sed "s/ngx_pagespeed_etag_filter//" \
+                           | sed "s/ngx_http_range_header_filter_module/ngx_http_range_header_filter_module ngx_pagespeed_etag_filter/")
+    else
+      # config.make is not executed for dynamic modules
+      CFLAGS="$CFLAGS -Wno-c++11-extensions"
+      if [ "$position_aux" = "true" ] ; then
+        ngx_module_type=HTTP_AUX_FILTER
+        ngx_module_order=""
+      fi
+    fi
+else
+  CORE_LIBS="$CORE_LIBS $pagespeed_libs"
+  CORE_INCS="$CORE_INCS $pagespeed_include"
+  NGX_ADDON_SRCS="$PS_NGX_SRCS"
+  if [ "$position_aux" = "true" ] ; then
+    HTTP_AUX_FILTER_MODULES="$HTTP_AUX_FILTER_MODULES $ngx_addon_name"
+  else
+    HTTP_FILTER_MODULES=$(echo $HTTP_FILTER_MODULES | sed "s/$next/$next $ngx_addon_name/")
   fi
 
   # Make the etag header filter run immediately before range header filter.
   HTTP_FILTER_MODULES=$(echo $HTTP_FILTER_MODULES |\
     sed "s/ngx_http_range_header_filter_module/ngx_http_range_header_filter_module ngx_pagespeed_etag_filter/")
-
-  CORE_LIBS="$CORE_LIBS $pagespeed_libs"
-  CORE_INCS="$CORE_INCS $pagespeed_include"
-  echo "List of modules (in reverse order of applicability): "$HTTP_FILTER_MODULES
-else
-  cat << END
-$0: error: module ngx_pagespeed requires the pagespeed optimization library.
-Look in obj/autoconf.err for more details.
-END
-  exit 1
 fi
 
+echo "List of modules (in reverse order of applicability): "$HTTP_FILTER_MODULES
+
 # Test whether the compiler is compatible
 ngx_feature="psol-compiler-compat"
 ngx_feature_name=""