Fix crypt.tex with newer TeXLive (thanks Norbert Preining)

See https://lists.debian.org/debian-tex-maint/2017/08/msg00000.html for details

doc/crypt.tex

@@ -1,5 +1,5 @@
 \documentclass[synpaper]{book}
-\usepackage[dvips]{geometry}
+\usepackage{geometry}
 \usepackage{hyperref}
 \usepackage{makeidx}
 \usepackage{amssymb}