C: add Filippo Valsorda's cloudflare.com email (Cloudflare CLA)

Change-Id: I98d265bfa4f5944360d0258d2cb6bbc78010c708
Reviewed-on: https://go-review.googlesource.com/44731Reviewed-by: Ian Lance Taylor <iant@golang.org>

CONTRIBUTORS

@@ -409,7 +409,7 @@ Fazlul Shahriar <fshahriar@gmail.com>
 Federico Simoncelli <fsimonce@redhat.com>
 Fedor Indutny <fedor@indutny.com>
 Felix Geisendörfer <haimuiba@gmail.com>
-Filippo Valsorda <hi@filippo.io>
+Filippo Valsorda <filippo@cloudflare.com> <hi@filippo.io>
 Firmansyah Adiputra <frm.adiputra@gmail.com>
 Florian Uekermann <florian@uekermann-online.de> <f1@uekermann-online.de>
 Florian Weimer <fw@deneb.enyo.de>