Clang: Require LLVM/Clang >= 5.0.0

...for the code model parts and declare 5.0 as the supported version for
the clang static analyzer.

Adapt versions and tests, remove code assuming clang <= 5.0.

LLVM/Clang 5 was released on 07 Sep 2017.

Task-number: QTCREATORBUG-18931
Task-number: QTCREATORBUG-18657
Task-number: QTCREATORBUG-17187
Task-number: QTCREATORBUG-14881
Change-Id: I53b00258ca06a1d2e57f9379dacc54b310687295
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/tools/clangbackend/source/clangbackend_global.h

@@ -36,9 +36,4 @@ enum class PreferredTranslationUnit
     LastUninitialized,
 };
 
-// CLANG-UPGRADE-CHECK: Remove IS_SUSPEND_SUPPORTED once we require clang >= 5.0
-#if defined(CINDEX_VERSION_HAS_BACKPORTED_SUSPEND) || CINDEX_VERSION_MINOR >= 41
-#  define IS_SUSPEND_SUPPORTED
-#endif
-
 } // namespace ClangBackEnd

src/tools/clangbackend/source/clangdocumentsuspenderresumer.cpp

@@ -64,7 +64,6 @@ void categorizeHotColdDocuments(int hotDocumentsSize,
     }
 }
 
-#ifdef IS_SUSPEND_SUPPORTED
 static int hotDocumentsSize()
 {
     static int hotDocuments = -1;
@@ -108,17 +107,11 @@ static bool isResumable(const Document &document)
         && document.isVisibleInEditor();
 }
 
-#endif // IS_SUSPEND_SUPPORTED
-
 SuspendResumeJobs createSuspendResumeJobs(const std::vector<Document> &documents,
                                           int customHotDocumentSize)
 {
-    Q_UNUSED(documents);
-    Q_UNUSED(customHotDocumentSize);
-
     SuspendResumeJobs jobs;
 
-#ifdef IS_SUSPEND_SUPPORTED
     std::vector<Document> hotDocuments;
     std::vector<Document> coldDocuments;
 
@@ -134,7 +127,6 @@ SuspendResumeJobs createSuspendResumeJobs(const std::vector<Document> &documents
     const std::vector<Document> toResume = Utils::filtered(hotDocuments, &isResumable);
     for (const Document &document : toResume)
         jobs += createJobs(document, JobRequest::Type::ResumeDocument);
-#endif // IS_SUSPEND_SUPPORTED
 
     return jobs;
 }

src/tools/clangbackend/source/clangtranslationunit.cpp

@@ -108,12 +108,7 @@ TranslationUnitUpdateResult TranslationUnit::reparse(
 
 bool TranslationUnit::suspend() const
 {
-#ifdef IS_SUSPEND_SUPPORTED
     return clang_suspendTranslationUnit(cxTranslationUnit());
-#else
-    QTC_CHECK(false && "clang_suspendTranslationUnit() not supported.");
-    return false;
-#endif
 }
 
 TranslationUnit::CodeCompletionResult TranslationUnit::complete(