[AC 21.5] More texinfo 5.x changes

PATCH 21.5 Texinfo 5.2 whines at me every time I build info, because it expects every ＠node to have next, prev, and up pointers. Even worse, looking at the output shows that it tried to guess what the next, prev, and up pointers should be, and it doesn't always guess correctly. This patch is almost entirely just the addition of those pointers, plus fixing some confusion about whether the topmost node is spelled "top" or "Top". The exceptions are: - .hgignore: added man/Makefile (should have been part of my 25 Jun 2013 commit) - man/internals/internals.texi: fixed some damage to Ville's surname. The last letter of his surname plus the following space should be byte sequence 0xe4 0x20, but somehow we have the 3-byte sequence 0xe4 0xac 0xa0 there. - man/internals/internals.texi: texinfo 5.x doesn't like ＠enumerate followed by ＠itemize with no intervening ＠item. I just removed one layer to make texinfo happy. - man/lispref/customize.texi: moved a chunk of text to conform to the order given by the menus. - man/lispref/lispref.texi: used a ＠vskip instead of an empty ＠author to get some vertical space. - man/texinfo/{fdl,texinfo,version}.texi: synced up with the texinfo 5.2 release. - man/xemacs/custom.texi: did violence to some of Stephen's text. In particular, I heeded a comment and changed some ＠file{foo} to ＠uref{upstream for foo,foo}. Also imposed menus and sectioning commands on the Xft/fontconfig content. Stephen, is this part okay?