Do not update autorevision.h's time stamp if the content has not changed.

Also rewrite the driving script for more clarity.
Merge branch 'bugfixes' into 3.1
make -Cpo update-po
Pushing 3.1.0.
Update to release builds.
Bump netplay to a higher version (0x10).
Update win32's rc file.
Change version to 3.1.0