Include backtrace on Qt.

Should fix Symbian / Blackberry I expect.
Link backtrace on non-x86 via cmake.
Merge pull request #5219 from unknownbrackets/qt-fix

Include backtrace on Qt.
Not reschelding if voicesPlayingCount == 0
Improve comment about the sas delay
Fix a bug where changing resolution wouldn't make a difference on a fly
Not having voices playing is not an error. Disabling logging of it.
Merge pull request #5225 from DanyalZia/patch-50

Fix a bug where changing resolution wouldn't make a difference on the fly