Refactor rct_track_preview flags (#10906)

* Refactor rct_track_preview flags

* Zero-index rct_track_preview flags

src/openrct2-ui/windows/RideConstruction.cpp

@@ -2368,7 +2368,7 @@ static void window_ride_construction_draw_track_piece(
         trackBlock++;
 
     CoordsXYZ mapCoords{ trackBlock->x, trackBlock->y, trackBlock->z };
-    if (trackBlock->var_09 & 2)
+    if (trackBlock->flags & RCT_PREVIEW_TRACK_FLAG_1)
     {
         mapCoords.x = 0;
         mapCoords.y = 0;

src/openrct2/actions/TrackPlaceAction.hpp

@@ -213,7 +213,7 @@ public:
             int32_t baseZ = mapLoc.z;
 
             int32_t clearanceZ = trackBlock->var_07;
-            if (trackBlock->var_09 & (1 << 2) && RideData5[ride->type].clearance_height > 24)
+            if (trackBlock->flags & RCT_PREVIEW_TRACK_FLAG_IS_VERTICAL && RideData5[ride->type].clearance_height > 24)
             {
                 clearanceZ += 24;
             }
@@ -453,7 +453,7 @@ public:
             auto quarterTile = trackBlock->var_08.Rotate(_origin.direction);
 
             int32_t clearanceZ = trackBlock->var_07;
-            if (trackBlock->var_09 & (1 << 2) && RideData5[ride->type].clearance_height > 24)
+            if (trackBlock->flags & RCT_PREVIEW_TRACK_FLAG_IS_VERTICAL && RideData5[ride->type].clearance_height > 24)
             {
                 clearanceZ += 24;
             }

src/openrct2/ride/Track.h

@@ -38,7 +38,7 @@ struct rct_preview_track
     int16_t z;     // 0x05
     uint8_t var_07;
     QuarterTile var_08;
-    uint8_t var_09;
+    uint8_t flags;
 };
 
 /* size 0x0A */
@@ -52,6 +52,13 @@ struct rct_track_coordinates
     int16_t y;             // 0x08
 };
 
+enum
+{
+    RCT_PREVIEW_TRACK_FLAG_0 = (1 << 0),
+    RCT_PREVIEW_TRACK_FLAG_1 = (1 << 1),
+    RCT_PREVIEW_TRACK_FLAG_IS_VERTICAL = (1 << 2),
+};
+
 enum
 {
     TRACK_ELEMENT_FLAG_TERMINAL_STATION = 1 << 3,