While freezero() returns early if the pointer is NULL the tests for
NULL in callers are left to avoid warnings about passing an
uninitialised size argument across a function boundry.
ok deraadt@ djm@
OpenBSD-Commit-ID: 2660fa334fcc7cd05ec74dd99cb036f9ade6384a
Add #ifdef WITH_XMSS to ssh-xmss.c, move it in the other files to after
includes.h so it's less likely to conflict and will pick up WITH_XMSS if
added to config.h.