Add system include path to HeaderPath and merge ProjectPartHeaderPath

System include paths are appended after other includes by the compiler. So
we should set them as system includes and not as normal includes. Otherwise
we change the include order. Headers in system include paths are not
cluttering the screen with unwanted warning and by the way improve
performance too.

ProjectPartHeaderPath was a dopperganger of HeaderPath, so we merged them.

Change-Id: I7c394b4098b697de79761499ffcd5913cc02d652
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/cpptools/cppsourceprocessor_test.cpp

@@ -47,6 +47,7 @@ using namespace CPlusPlus;
 using namespace CppTools;
 using namespace CppTools::Tests;
 using namespace CppTools::Internal;
+using ProjectExplorer::IncludePathType;
 
 typedef Document::Include Include;
 
@@ -63,9 +64,9 @@ public:
     {
         QScopedPointer<CppSourceProcessor> sourceProcessor(
                     CppModelManager::createSourceProcessor());
-        const ProjectPartHeaderPath hp(TestIncludePaths::directoryOfTestFile(),
-                                       ProjectPartHeaderPath::IncludePath);
-        sourceProcessor->setHeaderPaths(ProjectPartHeaderPaths() << hp);
+        const ProjectExplorer::HeaderPath hp(TestIncludePaths::directoryOfTestFile(),
+                                             IncludePathType::User);
+        sourceProcessor->setHeaderPaths({hp});
         sourceProcessor->run(filePath);
 
         Document::Ptr document = m_cmm->document(filePath);
@@ -207,9 +208,8 @@ void CppToolsPlugin::test_cppsourceprocessor_includeNext()
 
     CppSourceProcessor::DocumentCallback documentCallback = [](const Document::Ptr &){};
     CppSourceProcessor sourceProcessor(Snapshot(), documentCallback);
-    ProjectPartHeaderPaths headerPaths = ProjectPartHeaderPaths()
-        << ProjectPartHeaderPath(customHeaderPath, ProjectPartHeaderPath::IncludePath)
-        << ProjectPartHeaderPath(systemHeaderPath, ProjectPartHeaderPath::IncludePath);
+    ProjectExplorer::HeaderPaths headerPaths = {{customHeaderPath, IncludePathType::User},
+                                          {systemHeaderPath, IncludePathType::User}};
     sourceProcessor.setHeaderPaths(headerPaths);
 
     sourceProcessor.run(mainFilePath);