Some cleanup in the C++ preprocessor.

Introduced pp-scanner.cpp, renamed `pp' to `Preprocessor' and removed useless #includes.

src/libs/cplusplus/pp.h

@@ -50,15 +50,9 @@
   CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
-#ifndef PP_H
-#define PP_H
+#ifndef CPLUSPLUS_PREPROCESSOR_H
+#define CPLUSPLUS_PREPROCESSOR_H
 
-#include <cassert>
-#include <cstring>
-#include <cctype>
-
-#include "pp-cctype.h"
-#include "pp-internal.h"
 #include "pp-macro.h"
 #include "pp-environment.h"
 #include "pp-scanner.h"
@@ -66,4 +60,4 @@
 #include "pp-engine.h"
 #include "pp-client.h"
 
-#endif // PP_H
+#endif // CPLUSPLUS_PREPROCESSOR_H