add notes

llvm-svn: 38859
diff --git a/clang/README.txt b/clang/README.txt
index 7813ea2..adedd40 100644
--- a/clang/README.txt
+++ b/clang/README.txt
@@ -77,6 +77,9 @@
 Traditional Preprocessor:
  * All.
 
+Parser:
+ * C90/K&R modes.  Need to get C90 spec.
+
 Parser Callbacks:
  * Enough to do devkit-style "indexing".
  * All.