IR: Preserve use-list order by default in bitcode

Pull the `-preserve-*-use-list-order` flags out of "experimental" mode,
and preserve use-list order by default when serializing to bitcode.

llvm-svn: 234510
diff --git a/llvm/lib/IR/UseListOrder.cpp b/llvm/lib/IR/UseListOrder.cpp
index d064e67..a636310 100644
--- a/llvm/lib/IR/UseListOrder.cpp
+++ b/llvm/lib/IR/UseListOrder.cpp
@@ -18,12 +18,12 @@
 
 static cl::opt<bool> PreserveBitcodeUseListOrder(
     "preserve-bc-use-list-order",
-    cl::desc("Experimental support to preserve bitcode use-list order."),
-    cl::init(false), cl::Hidden);
+    cl::desc("Preserve use-list order when writing LLVM bitcode."),
+    cl::init(true), cl::Hidden);
 
 static cl::opt<bool> PreserveAssemblyUseListOrder(
     "preserve-ll-use-list-order",
-    cl::desc("Experimental support to preserve assembly use-list order."),
+    cl::desc("Preserve use-list order when writing LLVM assembly."),
     cl::init(false), cl::Hidden);
 
 bool llvm::shouldPreserveBitcodeUseListOrder() {