Fix compilation with gcc

Fix error:

../../../src/CppParser/AST.cpp:566:21: error: ‘MacroLocation’ is not a
class, namespace, or enumeration
       MacroLocation(MacroLocation::Unknown) {}

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@iki.fi>

src/CppParser/AST.cpp

@@ -563,7 +563,7 @@ Namespace::Namespace()
 
 PreprocessedEntity::PreprocessedEntity()
     : Declaration(DeclarationKind::PreprocessedEntity),
-      MacroLocation(MacroLocation::Unknown) {}
+      MacroLocation(AST::MacroLocation::Unknown) {}
 
 MacroDefinition::MacroDefinition() { Kind = DeclarationKind::MacroDefinition; }