Allow checks access to the SourceManager

 * This modification of the Clang-tidy basic headers
   seems to be the only way to get access to the SourceManager
   from within the checks
 * Reason: I would like to be able to analyse locations independent
           of the diag() function

Author: sawenzel

ClangTidyDiagnosticConsumer.h

@@ -151,6 +151,11 @@ class ClangTidyContext {
   /// This is called from the \c ClangTidyCheck base class.
   void setSourceManager(SourceManager *SourceMgr);
 
+  /// \brief Allow checks to access the SourceManager directly
+  ///
+  SourceManager &getSourceManager() const { return DiagEngine->getSourceManager(); }
+
+
   /// \brief Should be called when starting to process new translation unit.
   void setCurrentFile(StringRef File);