Add a utility function fsCasePreserving.

Returns true if the underlying file system is case preserving instead
of case sensitive. That is true for Mac and Windows currently. Only
Linux has a case sensitive file system usually.

src/mirall/utility.cpp

@@ -348,6 +348,15 @@ static bool checkDolphinCanSelect()
     return p.readAll().contains("--select");
 }
 
+bool Utility::fsCasePreserving()
+{
+    bool re = false;
+    if( isWindows() || isMac() ) {
+        re = true;
+    }
+    return re;
+}
+
 // inspired by Qt Creator's showInGraphicalShell();
 void Utility::showInFileManager(const QString &localPath)
 {

src/mirall/utility.h

@@ -69,6 +69,12 @@ namespace Utility
     OWNCLOUDSYNC_EXPORT bool isUnix();
     OWNCLOUDSYNC_EXPORT bool isLinux(); // use with care
 
+    // Case preserving file system underneath?
+    // if this function returns true, the file system is case preserving,
+    // that means "test" means the same as "TEST" for filenames.
+    // if false, the two cases are two different files.
+    OWNCLOUDSYNC_EXPORT bool fsCasePreserving();
+
     class StopWatch {
     private:
         QHash<QString, quint64> _lapTimes;