remove subrequest test in range header, chunked, and header filters: they
are run after postpone filter which sends data only in main request context

src/http/modules/ngx_http_chunked_filter_module.c

diff --git a/src/http/modules/ngx_http_chunked_filter_module.c b/src/http/modules/ngx_http_chunked_filter_module.c
index 846053f..c3864bb 100644
--- a/src/http/modules/ngx_http_chunked_filter_module.c
+++ b/src/http/modules/ngx_http_chunked_filter_module.c
@@ -53,7 +53,6 @@
     if (r->headers_out.status == NGX_HTTP_NOT_MODIFIED
         || r->headers_out.status == NGX_HTTP_NO_CONTENT
         || r->headers_out.status == NGX_HTTP_CREATED
-        || r != r->main
         || (r->method & NGX_HTTP_HEAD))
     {
         return ngx_http_next_header_filter(r);

src/http/modules/ngx_http_range_filter_module.c

diff --git a/src/http/modules/ngx_http_range_filter_module.c b/src/http/modules/ngx_http_range_filter_module.c
index bc28408..3d9a38e 100644
--- a/src/http/modules/ngx_http_range_filter_module.c
+++ b/src/http/modules/ngx_http_range_filter_module.c
@@ -151,7 +151,6 @@
 
     if (r->http_version < NGX_HTTP_VERSION_10
         || r->headers_out.status != NGX_HTTP_OK
-        || r != r->main
         || r->headers_out.content_length_n == -1
         || !r->allow_ranges)
     {

src/http/ngx_http_header_filter_module.c

diff --git a/src/http/ngx_http_header_filter_module.c b/src/http/ngx_http_header_filter_module.c
index 0f6f173..6af0a8a 100644
--- a/src/http/ngx_http_header_filter_module.c
+++ b/src/http/ngx_http_header_filter_module.c
@@ -176,10 +176,6 @@
 
     r->header_sent = 1;
 
-    if (r != r->main) {
-        return NGX_OK;
-    }
-
     if (r->http_version < NGX_HTTP_VERSION_10) {
         return NGX_OK;
     }