MISC: Use header to place all precompiled headers

• Make this for CCLS to be happy
• Include this "precompiled header" everywhere
• Make includes from the src folder, and leave all ambiguity

src/Lib/Ass/Ass.hh

 #ifndef VIVY_ASS_ASS_H
 #define VIVY_ASS_ASS_H
 
-#include "Line.hh"
-#include "Syl.hh"
-#include "Style.hh"
-#include "AssPrivate.hh"
-#include "AssFactory.hh"
-#include "StyleProperties.hh"
+#include "Lib/Ass/Line.hh"
+#include "Lib/Ass/Syl.hh"
+#include "Lib/Ass/Style.hh"
+#include "Lib/Ass/AssPrivate.hh"
+#include "Lib/Ass/AssFactory.hh"
+#include "Lib/Ass/StyleProperties.hh"
 
 #endif // VIVY_ASS_ASS_H