Rename SymbolID to SymbolRef.  This is a precursor to some overhauling of the representation of symbolic values.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@60575 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/GRState.cpp b/lib/Analysis/GRState.cpp
index 83ab508..221ab06 100644
--- a/lib/Analysis/GRState.cpp
+++ b/lib/Analysis/GRState.cpp
@@ -7,7 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 //
-//  This file defines SymbolID, ExprBindKey, and GRState*
+//  This file defines SymbolRef, ExprBindKey, and GRState*
 //
 //===----------------------------------------------------------------------===//