- achieve hyperlinked page numbers in general index, despite xindy's
incompatibility with hyperref,
- obtain compatibility of pdflatex with xindy for documents with
Cyrillic scripts,
- use xindy by default with xelatex/lualatex because any non-ascii
character as first letter of an indexed term breaks PDF build if using
makeindex with lualatex, and produces incoherent index with xelatex.
This commit also switches off xindy logs (which were activated in parent
commits) as they are voluminous and not of immediate use to Sphinx user.
60b160431a
