MFen: Update the Mongolian translation of the Handbook.

1.170 -> 1.172 mn_MN.UTF-8/books/handbook/book.sgml
1.74 -> 1.75 mn_MN.UTF-8/books/handbook/desktop/chapter.sgml
1.77 -> 1.78 mn_MN.UTF-8/books/handbook/firewalls/chapter.sgml
1.442 -> 1.443 mn_MN.UTF-8/books/handbook/mirrors/chapter.sgml
1.119 -> 1.120 mn_MN.UTF-8/books/handbook/serialcomms/chapter.sgml
1.184 -> 1.185 mn_MN.UTF-8/books/handbook/x11/chapter.sgml

Submitted by: Ganbold Tsagaankhuu, ganbold at micom.mng.net