[htmlxref.cnf] Please update the list of Emacs manuals

[Thérèse Godefroy]

Hello,

A huge number of Emacs manuals are missing from htmlxref.cnf [0]. The 
attached diff tries to complete the list, based on the Emacs webpages 
[1]. I also updated the ada-mode URL.

Best regards,
Thérèse

[0] https://git.savannah.gnu.org/cgit/texinfo.git/tree/util/htmlxref.cnf
[1] https://www.gnu.org/software/emacs/manual/

htmlxref.diff
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