Fix format-security warnings
This patch should fix the FTBFS report in Debian sid (bug 997162): the format
string was omitted when displaying the message prefix and the mcabber version.
prefix=@prefix@
exec_prefix=@exec_prefix@
libdir=@libdir@
includedir=@includedir@
Name: MCabber
Description: Modular XMPP client
URL: http://mcabber.com
Requires.private: glib-2.0 gmodule-2.0 loudmouth-1.0
Version: @VERSION@
Libs:
Cflags: -I${includedir} @LIBOTR_CFLAGS@ @GPGME_CFLAGS@