Fix dividing 0 error in stress/cpp/microbench

Summary:
Per issue #2356, some CXX compilers may optimize away the
new/delete operation in stress/cpp/microbench.cpp.
Thus, this commit (1) bumps the time interval to 1 if it is 0, and
(2) modifies the pointers in the microbench to volatile.

test/stress/cpp/microbench.cpp

@@ -3,45 +3,45 @@
 
 static void
 malloc_free(void) {
-	void *p = malloc(1);
-	expect_ptr_not_null(p, "Unexpected malloc failure");
-	free(p);
+	void* volatile p = malloc(1);
+	expect_ptr_not_null((void *)p, "Unexpected malloc failure");
+	free((void *)p);
 }
 
 static void
 new_delete(void) {
-	auto p = ::operator new(1);
-	expect_ptr_not_null(p, "Unexpected new failure");
-	::operator delete(p);
+	void* volatile p = ::operator new(1);
+	expect_ptr_not_null((void *)p, "Unexpected new failure");
+	::operator delete((void *)p);
 }
 
 static void
 malloc_free_array(void) {
-	void *p = malloc(sizeof(int)*8);
-	expect_ptr_not_null(p, "Unexpected malloc failure");
-	free(p);
+	void* volatile p = malloc(sizeof(int)*8);
+	expect_ptr_not_null((void *)p, "Unexpected malloc failure");
+	free((void *)p);
 }
 
 static void
 new_delete_array(void) {
-	auto p = new int[8];
-	expect_ptr_not_null(p, "Unexpected new[] failure");
-	delete[] p;
+	int* volatile p = new int[8];
+	expect_ptr_not_null((int *)p, "Unexpected new[] failure");
+	delete[] (int *)p;
 }
 
 #if __cpp_sized_deallocation >= 201309
 static void
 new_sized_delete(void) {
-	auto p = ::operator new(1);
-	expect_ptr_not_null(p, "Unexpected new failure");
-	::operator delete(p, 1);
+	void* volatile p = ::operator new(1);
+	expect_ptr_not_null((void *)p, "Unexpected new failure");
+	::operator delete((void *)p, 1);
 }
 
 static void
 malloc_sdallocx(void) {
-	void *p = malloc(1);
-	expect_ptr_not_null(p, "Unexpected malloc failure");
-        sdallocx(p, 1, 0);
+	void* volatile p = malloc(1);
+	expect_ptr_not_null((void *)p, "Unexpected malloc failure");
+        sdallocx((void *)p, 1, 0);
 }
 #endif