I've downloaded Midori, and am attempting to build and install. According to the install instructions, I need to do this:

Make sure you have Python 2.4 or higher installed.

Change to the Midori folder on your
hard disk in a terminal.

Run './waf configure'

Run './waf build'

You can now run Midori from the build
folder like so

'./waf build --run'

Using --run as shown above will make
sure extensions as well as
localizations are used from the build
folder.

You can install it with './waf
install'

When I run configure, though, I get the following:

esther@esther-linux:~/midori-0.3.6$ ./waf configure

Checking for program gcc or cc           : /usr/bin/gcc 

Checking for program cpp                 : /usr/bin/cpp 

Checking for program ar                  : /usr/bin/ar 

Checking for program ranlib              : /usr/bin/ranlib 

Checking for gcc                         : ok  

Checking for program valac               : not found 

Vala is required for some extensions. 

Pass --disable-vala to not build with Vala. 

The instructions don't mention anything about Vala; what is it and where can I get it?