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/cmVariableRequiresCommand.cxx

@@ -22,7 +22,7 @@ bool cmVariableRequiresCommand
     return false;
     }
 
-  std::string testVariable = args[0]; 
+  std::string testVariable = args[0];
   if(!this->Makefile->IsOn(testVariable.c_str()))
     {
     return true;
@@ -38,7 +38,7 @@ bool cmVariableRequiresCommand
       requirementsMet = false;
       notSet += args[i];
       notSet += "\n";
-      cmCacheManager::CacheIterator it = 
+      cmCacheManager::CacheIterator it =
         this->Makefile->GetCacheManager()->GetCacheIterator(args[i].c_str());
       if(!it.IsAtEnd() && it.GetPropertyAsBool("ADVANCED"))
         {
@@ -47,7 +47,7 @@ bool cmVariableRequiresCommand
       }
     }
   const char* reqVar = this->Makefile->GetDefinition(resultVariable.c_str());
-  // if reqVar is unset, then set it to requirementsMet 
+  // if reqVar is unset, then set it to requirementsMet
   // if reqVar is set to true, but requirementsMet is false , then
   // set reqVar to false.
   if(!reqVar || (!requirementsMet && this->Makefile->IsOn(reqVar)))
@@ -58,14 +58,14 @@ bool cmVariableRequiresCommand
   if(!requirementsMet)
     {
     std::string message = "Variable assertion failed:\n";
-    message += testVariable + 
+    message += testVariable +
       " Requires that the following unset variables are set:\n";
     message += notSet;
     message += "\nPlease set them, or set ";
     message += testVariable + " to false, and re-configure.\n";
     if(hasAdvanced)
       {
-      message += 
+      message +=
         "One or more of the required variables is advanced."
         "  To set the variable, you must turn on advanced mode in cmake.";
       }