Add future for --run compiler flag.

This came out of discussion after chpl-run was committed.

r: bradcray

git-svn-id: svn+ssh://svn.code.sf.net/p/chapel/code/trunk@22413 3a8e244f-b0f2-452b-bcba-4c88e055c3ca
Update util/devel/README with chpl-run information.

r: vasslitvinov

git-svn-id: svn+ssh://svn.code.sf.net/p/chapel/code/trunk@22414 3a8e244f-b0f2-452b-bcba-4c88e055c3ca