C++: Always skip unknown preprocessor "directives"

Task-number: QTCREATORBUG-7780

Change-Id: Ie93704feff17ad8229e50fb1133048f2c7598dea
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: hjk <qthjk@ovi.com>

src/libs/cplusplus/pp-engine.cpp

@@ -1417,9 +1417,9 @@ void Preprocessor::handlePreprocessorDirective(PPToken *tk)
             handleElseDirective(tk, poundToken);
         else if (directive == ppElif)
             handleElifDirective(tk, poundToken);
-
-        skipPreprocesorDirective(tk);
     }
+
+    skipPreprocesorDirective(tk);
 }