Remove variable length arrays

These are not allowed in C++, and have been made optional in C11.
So let's just get rid of them and any issues they may cause.
diff --git a/tests/encperf.cxx b/tests/encperf.cxx
index 4e7038f..733d55b 100644
--- a/tests/encperf.cxx
+++ b/tests/encperf.cxx
@@ -423,8 +423,9 @@
   }
 
   int runCount = count;
-  struct stats runs[runCount];
-  double values[runCount], dev[runCount];
+  struct stats *runs = new struct stats[runCount];
+  double *values = new double[runCount];
+  double *dev = new double[runCount];
   double median, meddev;
 
   if (fn == NULL) {