scripts/setlocalversion: remove mercurial, svn and git-svn supports

The mercurial, svn, git-svn supports were added by the following commits:

 - 3dce174c ("kbuild: support mercurial in setlocalversion")

 - ba3d05fb ("kbuild: add svn revision information to setlocalversion")

 - ff80aa97

 ("setlocalversion: add git-svn support")

They did not explain why they are useful for the kernel source tree.
Let's revert all of them, and see if somebody will complain about it.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Nico Schottelius <nico-linuxsetlocalversion@schottelius.org>