OS X 10.10: LSSharedFileListItemResolve() is deprecated

LABEL: Mac
The current master emits this warning on OS X Yosemite Version 10.10:
```
qt/guiutil.cpp:699:9: warning: 'LSSharedFileListItemResolve' is deprecated: first deprecated in OS X 10.10 - Use LSSharedFileListItemCopyResolvedURL instead. [-Wdeprecated-declarations]
        LSSharedFileListItemResolve(item, resolutionFlags, &currentItemURL, __null);
        ^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Headers/LSSharedFileList.h:943:1: note: 'LSSharedFileListItemResolve' has been explicitly marked deprecated here
LSSharedFileListItemResolve(
^
1 warning generated.
```
Change the code to use the new semantics on the 10.10 and higher systems.