NestedMacroInstantiations -> NestedMacroExpansions

This is switches all the interfaces points (and most of the commenst
/ local variables I saw on my way through) regarding the
NestedMacroInstantiations bit.

The libclang enums corresponding to this state were renamed, but
a legacy enum was added with the old name, and the same value to keep
existing clients working. I've added a documentation blurb for it, but
let me know if there is a canonical way to document legacy elemenst of
the libclang interface.

No functionality changed here, even in tests.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@135141 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/c-index-test/c-index-test.c b/tools/c-index-test/c-index-test.c
index e574b87..6e0aaac 100644
--- a/tools/c-index-test/c-index-test.c
+++ b/tools/c-index-test/c-index-test.c
@@ -38,7 +38,7 @@
   if (getenv("CINDEXTEST_COMPLETION_CACHING"))
     options |= CXTranslationUnit_CacheCompletionResults;
   if (getenv("CINDEXTEST_NESTED_MACROS"))
-    options |= CXTranslationUnit_NestedMacroInstantiations;
+    options |= CXTranslationUnit_NestedMacroExpansions;
   
   return options;
 }