Replace all uses of bzero with memset. Bzero and memset are both

compiler built-ins so this change should not negatively effect the
generated code.  However, a forthcoming commit will remove the
implicit include of strings.h from stdlib.h and bzero will no longer
be visible in these translation units without additional includes.

Change-Id: I8080fbcaabad4ff280163515168e4af5cd0a7112