fix include style relating to cplusplus libraries

... and adjust INCLUDEPATH accordingly.

while i'm at messing with include statements, also re-order the include
blocks according to policy and sort them within bigger blocks.

Change-Id: I7762abfd7c4ecf59432b99db2f424e4fa25733a5
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/libs/cplusplus/SimpleLexer.cpp

@@ -29,10 +29,10 @@
 
 #include "SimpleLexer.h"
 
-#include "ObjectiveCTypeQualifiers.h"
+#include <cplusplus/ObjectiveCTypeQualifiers.h>
+#include <cplusplus/Lexer.h>
+#include <cplusplus/Token.h>
 
-#include <Lexer.h>
-#include <Token.h>
 #include <QDebug>
 
 using namespace CPlusPlus;