Improvements/Fixes to 14443 sniffing/snooping

- fixed a circular buffer rollover bug in iso14443a.c
- fixed 7 Byte UID handling in hf mf sniff
- fixed "cannot append" error in hf mf sniff d
- fixed hint on mfkey32 in hf mf sim x
- fixed hf mf sniff sometimes showing rogue data from previous calloc
- improve snooping/sniffing by syncing modulation detector window with reader signal (hi_iso14443a.v)
- code cleanup of hi_iso14443a.v


git-svn-id: http://proxmark3.googlecode.com/svn@852 ef4ab9da-24cd-11de-8aaa-f3a34680c41f