Set bsp_trace_t::surface.flags to surfaceFlags in server and game

Revert last commit so that grapple sky check is compatible with BSPC
BotImport_Trace in (removed from repo) code/bspc/be_aas_bspq3.c.

Set bsp_trace_t::surface.flags instead of surface.value to trace_t::surfaceFlags.
surface.flags is only used for the sky check for grapple AAS reachability.
surface.value is not used at all.

bsp_trace_t is not part of the game VM API, so this does not affect VM compatibility.
BotAI_Trace in game was changed to match server. surface.value/flags are not used in game.

code/botlib/be_aas_reach.c

@@ -3857,7 +3857,7 @@ int AAS_Reachability_Grapple(int area1num, int area2num)
 		//
 		bsptrace = AAS_Trace(start, NULL, NULL, end, 0, CONTENTS_SOLID);
 		//the grapple won't stick to the sky and the grapple point should be near the AAS wall
-		if ((bsptrace.surface.value & SURF_SKY) || (bsptrace.fraction * 500 > 32)) continue;
+		if ((bsptrace.surface.flags & SURF_SKY) || (bsptrace.fraction * 500 > 32)) continue;
 		//trace a full bounding box from the area center on the ground to
 		//the center of the face
 		VectorSubtract(facecenter, areastart, dir);