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/cmFileTimeComparison.h

@@ -31,7 +31,7 @@ public:
    *  Compare file modification times.
    *  Return true for successful comparison and false for error.
    *  When true is returned, result has -1, 0, +1 for
-   *  f1 older, same, or newer than f2.  
+   *  f1 older, same, or newer than f2.
    */
   bool FileTimeCompare(const char* f1, const char* f2, int* result);
 
@@ -42,7 +42,7 @@ public:
   bool FileTimesDiffer(const char* f1, const char* f2);
 
 protected:
-  
+
   cmFileTimeComparisonInternal* Internals;
 };