Fix some polling issues:

 - Don't background-poll disabled TAPs ... this was just a bug
   waiting to happen.  (And then it happened!)

 - Don't fail command line polls of disabled taps; that's not any
   kind of error, it's just that you can't do much.  But do show
   that tap-disabled status.

 - Spell "continuous" correctly in the variable name.  ;)

Not resolved by this patch:  the need for an interlock whereby
other code (like the JTAG layer) can block all other access to
the JTAG layer, e.g. while enabling or disabling TAPs.  And
that interlock needs to be timer-safe...


git-svn-id: svn://svn.berlios.de/openocd/trunk@2247 b42882b7-edfa-0310-969c-e2dbd0fdcd60