- Add getexecpath() support for OpenBSD

Index: mysys/my_getexe.c
--- mysys/my_getexe.c.orig
+++ mysys/my_getexe.c
@@ -17,7 +17,7 @@
 #include <my_sys.h>
 
 #ifdef _WIN32
-#elif defined(__linux__)
+#elif defined(__linux__) || (defined(__OpenBSD__) && defined(HAVE_GETEXECPATH))
 #include <unistd.h>
 #elif defined(__APPLE__)
 #include <libproc.h>
@@ -57,6 +57,9 @@ int my_get_exepath(char *buf, size_t size, const char 
 #elif defined(__NetBSD__)
   int mib[4] = {CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME };
   if (sysctl(mib, 4, buf, &size, NULL, 0) == 0)
+    return 0;
+#elif defined(__OpenBSD__) && defined(HAVE_GETEXECPATH)
+  if (getexecpath(buf, size) == 0)
     return 0;
 #endif
 
