Merge pull request #232 from cardinot/potentialBugs

Fix potential bugs and compiler warnings
Clean up vinyl prefs window.
Make lead-in time per deck.
logically dead code - conditional cannot be true
Merge pull request #233 from ywwg/vinyl-prefs-fixes

Clean up vinyl prefs window.
Move AutoDJ preferences out of interface and into a dedicated page.
logically dead code - unused flag
Missing break in switch - always show warning message
Nesting level does not match indentation - missing braces
Nesting level does not match indentation - add braces
Structurally dead code - code cannot be reached
Structurally dead code - remove unused/unreached 'return'
Unchecked return value - checks if resourceDir changed
Unchecked return value: writing cue file
Unchecked return value: reading ssflac file
Unchecked return value: checks query to select track locations
wrong parameter when apply master volume
avoid division by zero
wrong sizeof argument
Merge branch 'master' of https://github.com/mixxxdj/mixxx into potentialBugs