This a a prep-work for if and when we use gerrit
it is very important to call gerrit's commit-msg hook
and the sooner we teach our own hook to play nice with it
the less likely we will have issue during migration

This reverts commit 4001370b.

Conflicts:

	unusedcode.easy

It cannot be done at the main target, because there is no guarantee that
all help (or properties) files are in one directory.

This is necessary for C++ extensions (at least for those from sdext
module), because the manifest needs preprocessing (the extension's name
is platform-dependent etc.)