Let `missing' also work with versioned and prefixed programs. * lib/missing: Ignore prefixes of `gnu-', `gnu', and `g' when testing for known programs; also, ignore suffixes. * tests/missing.test: Amend test. * NEWS, THANKS: Update. Report by Tim Rice. Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>