Copy the valgrind.spec.in file from 2.4.0, which Jeremy wrote with this

Copy the valgrind.spec.in file from 2.4.0, which Jeremy wrote with this
commit message:

  Steal some magic from FC3's valgrind-2.2.0 .spec file; it would be nice
  to know if this works under other RPM-based distros (SuSE particularly).

I don't know much about .spec files, but this new version is much easier
to maintain because we don't have to list any filenames explicitly, and
no-one complained about it in 2.4.0, so let's go with it.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@4269