doc: make sure we use our own code for generating man pages
docutils would in some situations pick up its own manpage.py instead of
doc/manpage.py. Renaming to hgmanpage.py makes it less ambiguous.
#!/bin/sh
mkdir t
cd t
hg init
echo a > a
hg add a
hg commit -m test -d "1000000 0"
hg history
hg manifest --debug
hg cat a
hg verify