(svn r14611) -Fix (r13437)[FS#2421]: Store the age of a house in the map array instead of the construction year.
Note: Savegames from r13437 to now are broken and have a age of 255 years for a lot houses.

(svn r12060) -Fix: do not clear tiles when the town won't be able to build any buildings anyway
-Fix: allow building 2x2 building on slopes if not explicitly forbidden
-Fix: it was possible to build 2x1 and 1x2 buildings on slopes even if it was not allowed

(svn r9315) -Merge: The newhouses branch. With this merge comes almost complete support for
the newhouses grf specs, so all newhouses grfs will be playable in the game.

Many thanks to everyone who contributed code and ideas, and all the testers
who found things we missed.

(svn r7759) -Merge: makefile rewrite. This merge features:
- A proper ./configure, so everything needs to be configured only once, not for every make.
- Usage of makedepend when available. This greatly reduces the time needed for generating the dependencies.
- A generator for all project files. There is a single file with sources, which is used to generate Makefiles and the project files for MSVC.
- Proper support for OSX universal binaries.
- Object files for non-MSVC compiles are also placed in separate directories, making is faster to switch between debug and release compiles and it does not touch the directory with the source files.
- Functionality to make a bundle of all needed files for for example a nightly or distribution of a binary with all needed GRFs and language files.

Note: as this merge moves almost all files, it is recommended to make a backup of your working copy before updating your working copy.