Rename patch-scripts::exim_install to patch-aa without a repo-copy.
A continuum in the history for this file isn't necessary. What _is_
important is the purpose of the patch today:

*) Changes the test used to determine whether a file should be installed

to cope with files which we "touch" to zero bytes for packaging
purposes.

*) Causes the configure file to be installed as a sample only. The

administrator needs to rename this file to "activate" exim.

*) Changes the invocation of make-info to be less prone to fail on

silly errors and fixes the info(1) titles so that, for example
``info exim'' actually enters the exim.info file.