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/ \+$//'

Tests/StringFileTest/StringFile.cxx

@@ -26,6 +26,6 @@ int main(int, char*[])
   res += CheckMethod(relpath, "../../X11R6/bin/xnest");
   res += CheckMethod(configvar,
                      "@$@$junk =~ s/#$xyz#/$foo_bar{$wibble}->{$xyz}/;@@");
-  
+
   return res;
 }