If-Range support

src/http/ngx_http_request.c

diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
index 4b01906..c1dc3a6 100644
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -96,6 +96,10 @@
     { ngx_string("Range"), offsetof(ngx_http_headers_in_t, range),
                  ngx_http_process_header_line },
 
+    { ngx_string("If-Range"),
+                 offsetof(ngx_http_headers_in_t, if_range),
+                 ngx_http_process_unique_header_line },
+
     { ngx_string("Transfer-Encoding"),
                  offsetof(ngx_http_headers_in_t, transfer_encoding),
                  ngx_http_process_header_line },