repoman: fix use.stable, bug #456342

Make child package inherit stable status from the parent package.
This is required in order for USE deps of unstable packages to be
resolved correctly, since otherwise use.stable.{mask,force} settings
of dependencies may conflict (see bug #456342).
Check lib*/udev/rules.d for bug #455606.
#nowarn trick
try #nowarn with line ending
use if no in construction
if not typo fix