(svn r1355) -Fix: [1092473] random trees in scenario editor do not overwrite rocks as well

(svn r1354) Use WindowClass/WindowNumber to store/pass window class/number, not some arbitrary data types

(svn r1353) -Fix: [1092707] placing rocks in scenario editor. You can place rocks on trees and vice versa

(svn r1352) -Fix: [1093200] Drive side in new games. Setting the driver side is possible during the game until someone buys road vehicles. In networked games only the server can change it.

(svn r1351) fixed issue in last commit where it it not update the replace train window properly when changing company colour (the lower two panels stayed the old colour until the window was reopened)

(svn r1350) Replace Vehicle GUI:
- Replaced "WP(w,replaceveh_d).line_height" with
"w->resize.step_height" since they needed to be the same anyway
- Cleaned the code a litte for readability (like correct tabbing)
- Added company color to replace vehicle windows to make them look like
the rest of the vehicle windows and made the caption text white (also to
fit the standard)

--This line, and those below, will be ignored--

M vehicle_gui.c
M lang/english.txt
M window.h

(svn r1349) -Fix: [1093485] Dissappearing rocks in Scenario Editor

(svn r1348) -Feature: resizable windows. Read the comment in window.h to find out
how the system works. All useful windows are already made resizable. Enjoy :)
-Fix: fixed some GUI-glitches and flaws along the way

(svn r1347) -Fix: Some were fixed for the trees -> Only copy the lowest two bits (amount of snow/desert) from map5 to map2 when placing trees, before this happened implicitly because map2 was just 8 bits wide;

(svn r1346) -Fix: fix signed/unsigned warnings
-Fix: latent removal of 2 lines from ttd.c which I forgot because the file was not saved :O