Improved timeout logic in quartzplugin

When GKSTerm is in the background, its response time can vary wildly and it
can exceed the current 50ms timeout. The changes in this commit reduce the
time between checking for a response from 10ms to 1ms and increase the timeout
for the GKSTerm 'is running' response from 50ms to 500ms after the first
succesful 'is running' check.

lib/gks/plugin/quartzplugin.m

@@ -37,8 +37,10 @@ DLLEXPORT void gks_quartzplugin(int fctid, int dx, int dy, int dimx, int *i_arr,
 #endif
 
 #define GKSTERM_DEFAULT_TIMEOUT 5000
+
+static int gksterm_has_run_before = 0;
 /* Timeout for is running is short so that GKSTerm will be started quickly. */
-#define GKSTERM_IS_RUNNING_TIMEOUT 50
+#define GKSTERM_IS_RUNNING_TIMEOUT (gksterm_has_run_before ? 500 : 50)
 
 static gks_state_list_t *gkss;
 
@@ -93,7 +95,7 @@ static void gksterm_communicate(const char *request, size_t request_len, int tim
         }
       if (rc == -1 && errno == EAGAIN)
         {
-          usleep(10000);
+          usleep(1000);
         }
       rc = zmq_msg_send(&message, socket, ZMQ_DONTWAIT);
     }
@@ -115,7 +117,7 @@ static void gksterm_communicate(const char *request, size_t request_len, int tim
         }
       if (rc == -1 && errno == EAGAIN)
         {
-          usleep(10000);
+          usleep(1000);
         }
       rc = zmq_msg_recv(&message, socket, ZMQ_DONTWAIT);
     }
@@ -148,6 +150,7 @@ static bool gksterm_is_running()
     {
       return false;
     }
+  gksterm_has_run_before = 1;
   return true;
 }