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/include/clang-c/Index.h b/include/clang-c/Index.h
index 858b2ce..b9197b8 100644
--- a/include/clang-c/Index.h
+++ b/include/clang-c/Index.h
@@ -840,7 +840,17 @@
    * a large amount of storage to due preprocessor metaprogramming. Moreover,
    * its fairly rare that this information is useful for libclang clients.
    */
-  CXTranslationUnit_NestedMacroInstantiations = 0x40
+  CXTranslationUnit_NestedMacroExpansions = 0x40,
+
+  /**
+   * \brief Legacy name to indicate that the "detailed" preprocessing record,
+   * if requested, should contain nested macro instantiations.
+   *
+   * \see CXTranslationUnit_NestedMacroExpansions for the current name for this
+   * value, and its semantics. This is just an alias.
+   */
+  CXTranslationUnit_NestedMacroInstantiations =
+    CXTranslationUnit_NestedMacroExpansions
 };
 
 /**