do not disable gzip for MSIE 6.0 SV1 in "gzip_disable msie6"

src/http/ngx_http_request.c

diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
index 5f46e61..187310b 100644
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -1386,8 +1386,13 @@
                 r->headers_in.msie4 = 1;
                 /* fall through */
             case '5':
-            case '6':
                 r->headers_in.msie6 = 1;
+                break;
+            case '6':
+                if (ngx_strstrn(msie + 8, "SV1", 3 - 1) == NULL) {
+                    r->headers_in.msie6 = 1;
+                }
+                break;
             }
         }