Make reedmace grow faster (was extremely slow...)

At the previous rate, it would take almost 2 days and 15 hours of
playing time for half of the reedmace to grow. (and therefore 5 days
and 6 hours for 75% to grow, etc.)

The new rate should require 2.25 hours of playing time for half of
the reedmace to grow.

dryplants/settings.txt

@@ -18,7 +18,7 @@ REEDMACE_FOR_OASES_PER_MAPBLOCK		=	35		-- plants per 80x80x80 nodes (absolute ma
 REEDMACE_FOR_OASES_RARITY			=	90		-- percent
 
 -- growing of reedmace sapling
-REEDMACE_GROWING_TIME 				= 	16800  	-- seconds
+REEDMACE_GROWING_TIME 				= 	600  	-- seconds
 REEDMACE_GROWING_CHANCE 			= 	5		-- percent