Globalize some of the main functions

This will allow to avoid nested 'dofile's

heightmap.lua

@@ -1,6 +1,5 @@
 local modpath = mapgen_rivers.modpath
 
-local make_polygons = dofile(modpath .. 'polygons.lua')
 local transform_quadri = dofile(modpath .. 'geometry.lua')
 
 local sea_level = mapgen_rivers.settings.sea_level
@@ -19,9 +18,9 @@ local function interp(v00, v01, v11, v10, xf, zf)
 	return v1*zf + v0*(1-zf)
 end
 
-local function heightmaps(minp, maxp)
+function mapgen_rivers.make_heightmaps(minp, maxp)
 
-	local polygons = make_polygons(minp, maxp)
+	local polygons = mapgen_rivers.make_polygons(minp, maxp)
 	local incr = maxp.z-minp.z+1
 
 	local terrain_height_map = {}
@@ -144,5 +143,3 @@ local function heightmaps(minp, maxp)
 
 	return terrain_height_map, lake_height_map
 end
-
-return heightmaps

init.lua

@@ -10,6 +10,8 @@ if minetest.get_mapgen_setting("mg_name") ~= "singlenode" then
 end
 
 dofile(modpath .. 'settings.lua')
+dofile(modpath .. 'polygons.lua')
+dofile(modpath .. 'heightmap.lua')
 
 local sea_level = mapgen_rivers.settings.sea_level
 local elevation_chill = mapgen_rivers.settings.elevation_chill
@@ -22,8 +24,6 @@ if use_biomegen_mod then
 	biomegen.set_elevation_chill(elevation_chill)
 end
 
-local heightmaps = dofile(modpath .. 'heightmap.lua')
-
 -- Linear interpolation
 local function interp(v00, v01, v11, v10, xf, zf)
 	local v0 = v01*xf + v00*(1-xf)
@@ -117,9 +117,9 @@ local function generate(minp, maxp, seed)
 		local pmaxp = {x=floor(xmax)+1, z=floor(zmax)+1}
 		incr = pmaxp.x-pminp.x+1
 		i_origin = 1 - pminp.z*incr - pminp.x
-		terrain_map, lake_map = heightmaps(pminp, pmaxp)
+		terrain_map, lake_map = mapgen_rivers.make_heightmaps(pminp, pmaxp)
 	else
-		terrain_map, lake_map = heightmaps(minp, maxp)
+		terrain_map, lake_map = mapgen_rivers.make_heightmaps(minp, maxp)
 	end
 
 	-- Check that there is at least one position that reaches min y

polygons.lua

@@ -119,7 +119,7 @@ local init = false
 
 -- On map generation, determine into which polygon every point (in 2D) will fall.
 -- Also store polygon-specific data
-local function make_polygons(minp, maxp)
+function mapgen_rivers.make_polygons(minp, maxp)
 
 	local grid = mapgen_rivers.grid
 	local dem = grid.dem
@@ -252,5 +252,3 @@ local function make_polygons(minp, maxp)
 
 	return polygons
 end
-
-return make_polygons