Time Attack respawn button: Specify hold behaviour

Now that TA wipes are their intended length, holding Respawn during Time Attack for more than a single frame repeatedly restarts the run. This is not ideal, and frankly wasteful of CPU. Here is the specified replacement for this case:
- Holding gc_respawn will hold on a black(/white) screen before mapload.
    - Allows for taking a conscious breather (or opportunity to curse) in the middle of long Time Attack sessions.
- Ticcmdbuilder will not interpret gc_respawn into BT_ constants in Time Attack contexts at all.
    - Fixes the occasionally visible E-Brake when coming out of this breather state.

src/g_build_ticcmd.cpp

@@ -404,7 +404,10 @@ class TiccmdBuilder
 		map(gc_item, BT_ATTACK); // fire
 
 		map(gc_lookback, BT_LOOKBACK); // rear view
-		map(gc_respawn, BT_RESPAWN | (freecam() ? 0 : BT_EBRAKEMASK)); // respawn
+		if (!modeattacking)
+		{
+			map(gc_respawn, BT_RESPAWN | (freecam() ? 0 : BT_EBRAKEMASK)); // respawn
+		}
 		map(gc_vote, BT_VOTE); // mp general function button
 
 		// lua buttons a thru c

src/k_menufunc.c

@@ -466,7 +466,7 @@ boolean M_Responder(event_t *ev)
 			if (Playing() && !demo.playback)
 			{
 				// Quick Retry (Y in modeattacking)
-				if (modeattacking && G_PlayerInputDown(0, gc_y, splitscreen + 1) == true)
+				if (modeattacking && G_PlayerInputDown(0, gc_respawn, splitscreen + 1) == true)
 				{
 					M_TryAgain(0);
 					return true;

src/p_setup.cpp

@@ -8681,6 +8681,38 @@ boolean P_LoadLevel(boolean fromnetsave, boolean reloadinggamestate)
 			}
 
 			F_RunWipe(wipetype, wipedefs[wipetype], false, ((levelfadecol == 0) ? "FADEMAP1" : "FADEMAP0"), false, false);
+
+			// Hold respawn to keep waiting until you're ready
+			if (G_IsModeAttackRetrying() && !demo.playback)
+			{
+				nowtime = lastwipetic;
+				while (G_PlayerInputDown(0, gc_respawn, splitscreen + 1) == true)
+				{
+					while (!((nowtime = I_GetTime()) - lastwipetic))
+					{
+						I_Sleep(cv_sleep.value);
+						I_UpdateTime();
+					} \
+
+					I_OsPolling();
+					G_ResetAllDeviceResponding();
+
+					for (; eventtail != eventhead; eventtail = (eventtail+1) & (MAXEVENTS-1))
+					{
+						HandleGamepadDeviceEvents(&events[eventtail]);
+						G_MapEventsToControls(&events[eventtail]);
+					}
+
+					lastwipetic = nowtime;
+					if (moviemode && rendermode == render_opengl)
+						M_LegacySaveFrame();
+					else if (moviemode && rendermode == render_soft)
+						I_CaptureVideoFrame();
+					NetKeepAlive();
+				}
+
+				//wipestyleflags |= (WSF_FADEOUT|WSF_TOWHITE);
+			}
 		}
 	}