optc-gen.awk (END): Make sure no variable is defined more than once.

optc-gen.awk (END): Make sure no variable is defined more than once.

* optc-gen.awk (END): Make sure no variable is defined more
than once.
* opth-gen.awk (END): Allocate bits on a per-variable basis.
Allow for bitfield variables other than target_flags.
* doc/options.text (Mask): Document that you may specify a
variable other than target_flags.

From-SVN: r98940