merge r3076, r3080:

fix segfault when a header starts with "\rX"
and logging is set to info or debug level
diff --git a/src/http/ngx_http_parse.c b/src/http/ngx_http_parse.c
index b83810d..de061c9 100644
--- a/src/http/ngx_http_parse.c
+++ b/src/http/ngx_http_parse.c
@@ -738,6 +738,7 @@
 
         /* first char */
         case sw_start:
+            r->header_name_start = p;
             r->invalid_header = 0;
 
             switch (ch) {
@@ -750,7 +751,6 @@
                 goto header_done;
             default:
                 state = sw_name;
-                r->header_name_start = p;
 
                 c = lowcase[ch];