libfreerdp-codec: fix mppc decompression

* protect against history buffer overflows
* fix replicating copy (CopyOffset can be > HistoryBufferSize!)
core: use zero padding in suppress output pdu

Some legacy rdp servers seem to expect a zero padding after the
allowDisplayUpdates byte, probably because they incorrectly parse the
value as uint32.
Merge pull request #2210 from nfedera/fix-2014-11-14-01

core: use zero padding in suppress output pdu
Merge pull request #2206 from nfedera/fix-2014-11-12-01

libfreerdp-codec: fix mppc decompression