stdlib.h for malloc(3) and stdint.h for SIZE_MAX. Unlike the other xmss
files, ssh-xmss.c does not include xmss_commons.h so ssh-xmss.c must include
those headers itself. From Martin Vahlensieck
OpenBSD-Commit-ID: 70e28a9818cee3da1be2ef6503d4b396dd421e6b
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.
