(svn r3564) Several smaller changes:
- Don't treat non-booleans as booleans
- Reduce variable scope
- Bracing
- Use DeMorgan's law to make conditionals easier to read
- if cascade -> switch
- Replace some magic numbers by symbolic names
- Avoid assignments within other statements

(svn r3563) Simplify the code for calculating the highscore table in network games and saving of old ecenomy data

(svn r3562) Remove pointless buffer copies

(svn r3561) Don't use FindLandscapeHeightByTile() when it's overkill. Also use a sprite enum instead of a magic number.

(svn r3560) Restore plural forms of cargo types for several languages.
I extracted the info from 2614:2615.
If you speak one of the languages, please check if the changes are correct.

(svn r3559) - CodeChange: simplify MKCOLOR(x) macro for smallmap_gui.c by adding a TO_LE32X() macro next to TO_BE32X(). The 'X' signifies them as macros and not-inline functions so they can be used in variable declarations.

(svn r3558) Add newgrf_callbacks.h to VS project files

(svn r3557) - NewGRF: move callback enums to a new file as more than just engines will use them

(svn r3556) Add accessors for handling tree tiles
See tree.h for details

(svn r3555) -Codechange: [Big Endian] removed defining OTTD_ALIGNMENT by default on Big Endian CPUs
this increased speed when reading unaligned data (like strings)
test showed this to increase speed by 5,6% when drawing the mini map on PPC OSX

the tradeoff is that now it will crash if a Big Endian computer don't support unaligned reading
but it should easily fixable in stdafx.h if it turns out to be a problem