unlock an unlocked mutex result in crash in Qt5. wait is better

after tryLock returns false, it may be unlocked in demuxer thread before
unlock in mainn thread. in Qt5, it will crash. using a wait condition
for seeking is safe and seems better.
Qt5 building: QMimeData
version 1.1.8

Changelog
- LGPL version 2.1
- better Qt5 support
- better synchronisation and seeking
- crash fixed when getting stream info
- crash fixed when replaying a music
- drag & drop, simple internal gui and internal event filter
- videowall works better
player: use executable dir