work around Python warnings from AsciiDoc

work around Python warnings from AsciiDoc

It appears that a reference to an anchor defined as [[anchor-name]] from
another place using <<anchor-name>> syntax, when the anchor name contains
a string "-with-" in its name, triggers these warnings from Python
interpreter.

  asciidoc -b docbook -d book user-manual.txt
  <string>:1: Warning: 'with' will become a reserved keyword in Python 2.6
  <string>:1: Warning: 'with' will become a reserved keyword in Python 2.6
  <string>:1: Warning: 'with' will become a reserved keyword in Python 2.6
  <string>:1: Warning: 'with' will become a reserved keyword in Python 2.6

There currently is no reference to "Finding comments with given content",
but for consistency and for futureproofing, the anchor is also updated as
the other ones that are actually used and trigger these warnings.

Signed-off-by: Junio C Hamano <junio@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>