This reverts 5da3337c "readded include stdlib.h,
because of missing NULL definition in many headers, #100000, #101685", which is
no longer relevant.

Change-Id: I544ed9a7afbf7b611bc481b8d50acca3193d93de
Reviewed-on: https://gerrit.libreoffice.org/48131Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
Tested-by: Stephan Bergmann <sbergman@redhat.com>