Fix for bug: [#8269] Particle / Vizualization / Draw / Disp reduces rendered particles

- Hair didn't update the visibility flag of each particle
- Changing the disp value gave a too strong update call to particles
- Changed disp value behavior for dynamic particles a bit, now all particles are always calculated for uncached frames so that every particle gets it's data cached. Now the disp value actually does what it's supposed to do, it alters the amount of particles DISPlayed in viewport, but doesn't change the simulations. (With old particles it was possible to only calculate the disp amount of particles too as everything was always recalculated from scratch anyways, but now that particles are more complicated and cached etc. it's not an option anymore.)

source/blender/src/buttons_object.c

@@ -4244,7 +4244,7 @@ static void object_panel_particle_visual(Object *ob)
 	uiDefButBitS(block, TOG, PART_DRAW_SIZE, B_PART_REDRAW, "Size",	butx+butw/3,buty,butw/3,buth, &part->draw, 0, 0, 0, 0, "Show particle size");
 	uiDefButBitS(block, TOG, PART_DRAW_NUM, B_PART_REDRAW, "Num",	butx+2*butw/3,buty,butw/3,buth, &part->draw, 0, 0, 0, 0, "Show particle number");
 	uiDefButS(block, NUM, B_PART_REDRAW, "Draw Size:", butx,(buty-=buth),butw,buth, &part->draw_size, 0.0, 10.0, 0, 0, "Size of particles on viewport in pixels (0=default)");
-	uiDefButS(block, NUM, B_PART_RECALC, "Disp:",		butx,(buty-=buth),butw,buth, &part->disp, 0.0, 100.0, 10, 0, "Percentage of particles to calculate for 3d view");
+	uiDefButS(block, NUM, B_PART_RECALC_CHILD, "Disp:",		butx,(buty-=buth),butw,buth, &part->disp, 0.0, 100.0, 10, 0, "Percentage of particles to display in 3d view");
 	uiBlockEndAlign(block);
 
 	uiDefBut(block, LABEL, 0, "Render:",	butx,(buty-=buth),butw,buth, NULL, 0.0, 0, 0, 0, "");