Unconditional compilation of the postpone filter.

Postpone filter is an essential part of subrequest functionality.  In absence
of it a subrequest response body is sent to the client out of order with
respect to the main request header and body, as well as other subrequests.
For in-memory subrequests the response is also sent to the client instead of
being stored in memory.

Currently the postpone filter is automatically enabled if one of the following
standard modules which are known to create subrequests is enabled: ssi, slice,
addition.  However a third-party module that creates subrequests can still be
built without the postpone filter or be dynamically loaded in nginx built
without it.

auto/modules

diff --git a/auto/modules b/auto/modules
index 09bfcb0..d78e282 100644
--- a/auto/modules
+++ b/auto/modules
@@ -102,21 +102,6 @@
     fi
 
 
-    if [ $HTTP_SSI = YES ]; then
-        HTTP_POSTPONE=YES
-    fi
-
-
-    if [ $HTTP_SLICE = YES ]; then
-        HTTP_POSTPONE=YES
-    fi
-
-
-    if [ $HTTP_ADDITION = YES ]; then
-        HTTP_POSTPONE=YES
-    fi
-
-
     # the module order is important
     #     ngx_http_static_module
     #     ngx_http_gzip_static_module
@@ -252,13 +237,13 @@
         . auto/module
     fi
 
-    if [ $HTTP_POSTPONE = YES ]; then
+    if :; then
         ngx_module_name=ngx_http_postpone_filter_module
         ngx_module_incs=
         ngx_module_deps=
         ngx_module_srcs=src/http/ngx_http_postpone_filter_module.c
         ngx_module_libs=
-        ngx_module_link=$HTTP_POSTPONE
+        ngx_module_link=YES
 
         . auto/module
     fi

auto/options

diff --git a/auto/options b/auto/options
index d8b421b..521c976 100644
--- a/auto/options
+++ b/auto/options
@@ -60,7 +60,6 @@
 HTTP_SSL=NO
 HTTP_V2=NO
 HTTP_SSI=YES
-HTTP_POSTPONE=NO
 HTTP_REALIP=NO
 HTTP_XSLT=NO
 HTTP_IMAGE_FILTER=NO