Remove use of builtin comma operator.

Cleanup for upcoming Clang warning -Wcomma.  No functionality change intended.

llvm-svn: 261271
diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index e304965..350f16d 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -980,7 +980,8 @@
             << SourceRange(CR->getLHS()->getLocStart(),
                            Hi->getLocEnd());
           CaseRanges.erase(CaseRanges.begin()+i);
-          --i, --e;
+          --i;
+          --e;
           continue;
         }