criu(1): man page title should be in UPPERCASE

It's a common practice.
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Documentation/criu.txt

-criu(1)
+CRIU(1)
 =======
 :doctype:       manpage
 :man source:    criu