Unbreak isolationtester on Win32

I broke it in a previous commit because I neglected to install the
necessary incantations to have getopt() work on Windows.

Per red blots in buildfarm.

src/test/isolation/isolationtester.c

@@ -14,6 +14,13 @@
 #ifndef WIN32
 #include <sys/time.h>
 #include <unistd.h>
+
+#ifdef HAVE_GETOPT_H
+#include <getopt.h>
+#endif
+
+#else
+int			getopt(int argc, char *const argv[], const char *optstring);
 #endif   /* ! WIN32 */
 
 #ifdef HAVE_SYS_SELECT_H
@@ -25,6 +32,8 @@
 
 #include "isolationtester.h"
 
+extern int	optind;
+
 #define PREP_WAITING "isolationtester_waiting"
 
 /*