Tried the same thing with the 2.0.5 source TGZ, with the exact same result.
Here you can read the output of the make command: http://pastebin.com/f48d9c88f

Please provide a whole transcript of you're trying to compile it.

You mean every step I took, including the installation of XAMPP?

I don't really care about XAMPP... if you think it's useful, include it anyway.

Step 1: Downloaded the 2.0.5 TGZ file from the website, which was saved to /home/WebDevHobo/Downloads/

Step 2: Opened a terminal, execute command "sudo su -" to execute further actions as root.

Step 3: Navigate to the Downloads folders, execute the command: "tar -xzf xdebug-2.0.5.tgz -C /opt"

Step 4: Navigate to the /opt/xdebug-2.0.5/ folder.

Step 5: Execute the command "/opt/lampp/bin/phpize-5.3.1". Output can be viewed here: http://pastebin.com/f4e59b341

Step 6: Execute the command "./configure --enable-xdebug --with-php-config=/opt/lampp/bin/php-config-5.3.1". Output can be viewed here: http://pastebin.com/f354ae151

Step 7: Execute the command "make". Output van be viewed here: http://pastebin.com/f1eaba535

And that's where I'm stuck. The created modules folder, needed in the next step, is empty.

I'm signing off for today.

I think that you're missing the php5-dev package. php.h and php_version.h look like they're missing on your system and are provided by php5-dev.

Thanks, problem resolved.

For future reference, the steps taken to solve this were:

1) Become root at the command line by use of the command "sudo su -"

2) Remove the old folder: "rm -r /opt/xdebug-2.0.5/"

3) Do a fresh tar of the file: "tar -xfz /path/to/xdebug.tar -C /opt".

4) Install php5-dev: "apt-get install php5-dev"

5) Navigate to the /opt/xdebug-2.0.5 folder

6) Execute the command: "/usr/bin/phpize5"

7) Execute the command: "./configure --enable-xdebug" (MUST be done from within the /opt/xdebug-2.0.5 folder)

8) Execute the command: "make"

And it worked. I then copied xdebug.so to /opt/lampp/lib

All that is left is to add this code:
zend_extension=/opt/lampp/lib/xdebug.so
xdebug.remote_enable=On
xdebug.remote_host="localhost"
xdebug.remote_port=9000
xdebug.remote_handler="dbgp"
xdebug.show_local_vars=On
xdebug.collect_return=On
xdebug.collect_params=4
xdebug.profiler_enable=On
xdebug.profiler_enable_trigger=1

To all php.ini files.

However, a new problem has risen.
When executing php -m, xdebug does show up in the Zend_Modules, but the phpinfo() result does not show it as active.

When trying to debug in Netbeans, with everything restarted and all php.ini files saved, there's no response, Netbeans just keeps waiting for the connection that never comes.

File a separate bug?

I uninstalled XAMPP and followed the instructions in this video: http://www.vimeo.com/8005503

Up to the point of Xdebug.
And hooray, everything works, I can debug succesfully with Netbeans.

I'm thinking the problem here was XAMPP, and no XDEBUG.