http2, push headers cleanup

[icing]

• provide common cleanup method for push headers

[danielgustafsson]

LGTM

[bagder]

I think it also needs this:

diff --git a/lib/http2.c b/lib/http2.c
index 2112545c5..725ec742c 100644
--- a/lib/http2.c
+++ b/lib/http2.c
@@ -1431,14 +1431,14 @@ static int on_header(nghttp2_session *session, const nghttp2_frame *frame,
         failf(data_s, "Too many PUSH_PROMISE headers");
         free_push_headers(stream);
         return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
       }
       stream->push_headers_alloc *= 2;
-      headp = Curl_saferealloc(stream->push_headers,
-                               stream->push_headers_alloc * sizeof(char *));
+      headp = realloc(stream->push_headers,
+                      stream->push_headers_alloc * sizeof(char *));
       if(!headp) {
-        stream->push_headers = NULL;
+        free_push_headers(stream);
         return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
       }
       stream->push_headers = headp;
     }
     h = aprintf("%s:%s", name, value);

[icing]

I think it also needs this:

Correct. Just added it. Thanks for finding.