installer: Add msys-rebase as a required package

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
Add a batch script to rebase all DLLs

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
installer: Optionally rebase DLLs as a post-install step

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>