add apt conf files for 5.1 repo

etc/apt/apt.conf.M51

+/*
+ * This is the main configuration file for the APT suite of tools,
+ * see apt.conf(5) for details.
+ */
+
+Dir::Etc::main "/dev/null";
+Dir::Etc::parts "/var/empty";
+Dir::Etc::SourceParts "/var/empty";
+
+Dir::Etc::sourcelist "/etc/eterbuild/apt/sources.list.M51";

etc/apt/sources.list.M51

+# Package repository URLs
+#
+# You can add [alt] after rpm for digital signature check
+
+rpm file:/var/ftp/ pub/ALTLinux/5.1/i586 classic
+rpm file:/var/ftp/ pub/ALTLinux/5.1/noarch classic
+rpm file:/var/ftp/ pub/ALTLinux/5.1/x86_32 classic
+
+#rpm file:/var/ftp/ pub/ALTLinux/updates/5.1/i586 updates
+#rpm file:/var/ftp/ pub/ALTLinux/backports/5.1/i586 backports