Remove trailing whitespaces

Many tools strip trailing whitespaces by default, so after editing a file with
whitespace errors we end up with a bunch of unrelated hunks that need to be
reverted locally.

This could be fixed by configuring each tool to not do this (at least for the
barrier repo), or, simpler, we just sed the problem away and make barrier
whitespace-compliant.

sed commands run:
    sed -i 's/[ \t]\+$//' **/*.(cpp|h) **/*CMakeLists.txt

Verified with git diff --ignore-space-change, this shows the empty diff.

src/lib/server/Server.h

@@ -2,11 +2,11 @@
  * barrier -- mouse and keyboard sharing utility
  * Copyright (C) 2012-2016 Symless Ltd.
  * Copyright (C) 2002 Chris Schoeneman
- * 
+ *
  * This package is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
  * found in the file LICENSE that should have accompanied this file.
- * 
+ *
  * This package is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
@@ -150,7 +150,7 @@ public:
 
     //! Store ClientListener pointer
     void                setListener(ClientListener* p) { m_clientListener = p; }
-    
+
     //@}
     //! @name accessors
     //@{
@@ -166,7 +166,7 @@ public:
     Set the \c list to the names of the currently connected clients.
     */
     void getClients(std::vector<std::string>& list) const;
-    
+
     //! Return true if recieved file size is valid
     bool                isReceivedFileSizeValid();
 
@@ -356,10 +356,10 @@ private:
 
     // force the cursor off of \p client
     void                forceLeaveClient(BaseClientProxy* client);
-    
+
     // thread funciton for sending file
     void                sendFileThread(void*);
-    
+
     // thread function for writing file to drop directory
     void                writeToDropDirThread(void*);
 
@@ -448,7 +448,7 @@ private:
     bool                m_switchNeedsShift;
     bool                m_switchNeedsControl;
     bool                m_switchNeedsAlt;
-    
+
     // relative mouse move option
     bool                m_relativeMoves;