Remove trailing whitespace from most CMake and C/C++ code

Our Git commit hooks disallow modification or addition of lines with
trailing whitespace.  Wipe out all remnants of trailing whitespace
everywhere except third-party code.

Run the following shell code:

git ls-files -z -- \
 bootstrap doxygen.config '*.readme' \
 '*.c' '*.cmake' '*.cpp' '*.cxx' \
 '*.el' '*.f' '*.f90' '*.h' '*.in' '*.in.l' '*.java' \
 '*.mm' '*.pike' '*.py' '*.txt' '*.vim' |
egrep -z -v '^(Utilities/cm|Source/(kwsys|CursesDialog/form)/)' |
egrep -z -v '^(Modules/CPack\..*\.in)' |
xargs -0 sed -i 's/ \+$//'

Source/cmExecProgramCommand.h

@@ -27,7 +27,7 @@ public:
   /**
    * This is a virtual constructor for the command.
    */
-  virtual cmCommand* Clone() 
+  virtual cmCommand* Clone()
     {
     return new cmExecProgramCommand;
     }
@@ -38,13 +38,13 @@ public:
    */
   virtual bool InitialPass(std::vector<std::string> const& args,
                            cmExecutionStatus &status);
-  
+
   /**
    * The name of the command as specified in CMakeList.txt.
    */
   virtual const char* GetName() const
     {return "exec_program";}
-  
+
   /**
    * This determines if the command is invoked when in script mode.
    */
@@ -55,10 +55,10 @@ public:
    */
   virtual const char* GetTerseDocumentation() const
     {
-    return 
+    return
       "Deprecated.  Use the execute_process() command instead.";
     }
-  
+
   /**
    * More documentation.
    */
@@ -82,7 +82,7 @@ public:
       "stdout/stderr of the console running cmake.\n"
       ;
     }
-  
+
   /** This command is kept for compatibility with older CMake versions. */
   virtual bool IsDiscouraged() const
     {