C: add Michael Kelly (Google CLA)

R=golang-codereviews, iant, mjk
CC=golang-codereviews
https://golang.org/cl/52220043

CONTRIBUTORS

@@ -348,6 +348,7 @@ Michael Elkins <michael.elkins@gmail.com>
 Michael Gehring <mg@ebfe.org> <gnirheg.leahcim@gmail.com>
 Michael Hoisie <hoisie@gmail.com>
 Michael Hudson-Doyle <michael.hudson@linaro.org>
+Michael Kelly <mjk@google.com>
 Michael Lewis <mikelikespie@gmail.com>
 Michael Matloob <matloob@google.com>
 Michael Piatek <piatek@google.com>