patch 8.2.2586: process id may be invalid

Problem:    Process id may be invalid.
Solution:   Use sysinfo.uptime to check for recent reboot. (suggested by Hugo
            van der Sanden, closes #7947)
diff --git a/src/globals.h b/src/globals.h
index 0fd08b6..cb3b4f4 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1860,6 +1860,7 @@
 EXTERN int  no_query_mouse_for_testing INIT(= FALSE);
 EXTERN int  ui_delay_for_testing INIT(= 0);
 EXTERN int  reset_term_props_on_termresponse INIT(= FALSE);
+EXTERN long override_sysinfo_uptime INIT(= -1);
 
 EXTERN int  in_free_unref_items INIT(= FALSE);
 #endif