Fixed several issues with the 6809

1. Interrupt/NMI were occasionally being missed because of lack of synchronization

2. Updated the CPU core to v126 from John Kent - this was found in Grant Searl's
   multicomp project: http://searle.hostei.com/grant/Multicomp/index.html

   Found a bug with the SYNC instruction that will be fixed in the next commit

3. Updated the clocking arrangement to that from the Z80

4. Updated the use of the test pins to o/p a clock plus A11..0 to maximise
   the number of address lines seen by the logic analyzer. Both edges of
   the clock should happen only on opfetch and only when the address bus is
   stable. This works well with my 1650A and has made it possible to debug
   issues with JGH's EXBAS09

Change-Id: If803be5ea0ccab60e0b324c8c0dbab15e1bbb1f1
Fixed a bug with the SYNC instruction not working in v126 of the SYS09 6809 core

Change-Id: I0ee5b296a5385d10e9aa2ce1fa2974ec173d7c63
Updated 6809 client ROM to a development snapshot of v0.23 taken on 4 Dec 2014

Change-Id: I7063983baa82d4ccb366a2a33038462570bebab4