Fix typo: s/Occurence/Occurrence/

This is a private class member so the fix shouldn't impact external projects.

llvm-svn: 195985
diff --git a/clang/tools/libclang/IndexingContext.cpp b/clang/tools/libclang/IndexingContext.cpp
index 952c255..2e0f7c2 100644
--- a/clang/tools/libclang/IndexingContext.cpp
+++ b/clang/tools/libclang/IndexingContext.cpp
@@ -802,9 +802,9 @@
   const FileEntry *FE = SM.getFileEntryForID(FID);
   if (!FE)
     return true;
-  RefFileOccurence RefOccur(FE, D);
-  std::pair<llvm::DenseSet<RefFileOccurence>::iterator, bool>
-  res = RefFileOccurences.insert(RefOccur);
+  RefFileOccurrence RefOccur(FE, D);
+  std::pair<llvm::DenseSet<RefFileOccurrence>::iterator, bool>
+  res = RefFileOccurrences.insert(RefOccur);
   if (!res.second)
     return true; // already in map.