This is subtle, but an unread marker is not an error unless we run out of bits, which...

This is subtle, but an unread marker is not an error unless we run out of bits, which may not occur in the same MCU in which the unread marker is encountered.  Thus, don't try to use the fast decoder as long as there is an outstanding unread marker.

git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.1.x@583 632fc199-4ca6-4c93-a231-07263d6284db