Fix a couple of incorrect format string warnings

This patch fixes use of incorrect `%zi` to format a plain `int`, and using
`%llu` to format a `uint64_t`. The fix is to use the new typesafe
`llvm::Formatv` based API.

Differential Revision: https://reviews.llvm.org/D28028
Subscribers: lldb-commits

llvm-svn: 290359
diff --git a/lldb/source/Interpreter/Args.cpp b/lldb/source/Interpreter/Args.cpp
index c428a23..6984328 100644
--- a/lldb/source/Interpreter/Args.cpp
+++ b/lldb/source/Interpreter/Args.cpp
@@ -213,10 +213,9 @@
   int i = 0;
   for (auto &entry : m_entries) {
     s.Indent();
-    s.Printf("%s[%zi]=\"%*s\"\n", label_name, i++, int(entry.ref.size()),
-             entry.ref.data());
+    s.Format("{0}[{1}]=\"{2}\"\n", label_name, i++, entry.ref);
   }
-  s.Printf("%s[%zi]=NULL\n", label_name, i);
+  s.Format("{0}[{1}]=NULL\n", label_name, i);
   s.EOL();
 }