[exim-dev] Release scripts: adjust version.h for RCs?

Nigel,

Since the release script is your baby, what do you feel about:
http://git.exim.org/users/pdp/review.git/commit/3cc515867dba168385161a5f8ebe6811ad7af974

That detects when the version being built is not a bare version (so,
_RC<n>) and adjusts version.h automatically as part of the preparation
process.

Look sane? Happy for me to commit?

-Phil