Update the jtag-examine_chain() logic to verify that there's no

Update the jtag-examine_chain() logic to verify that there's no
garbage after the expected data (from the TAPs' BYPASS or IDCODE
registers).

NOTE that there was previously some code that looked like it was
trying to do this ... which didn't work, because it was looping
over the list of expected TAPs, and never checked *after* that
list completed!  That could hide some *nasty* reset issues...

Also replace a now-obsolete scanchain length test with one that
behaves correctly; and update reporting of unexpected IDCODEs.

git-svn-id: svn://svn.berlios.de/openocd/trunk@2739 b42882b7-edfa-0310-969c-e2dbd0fdcd60