Unity/compiz fails to load on Intel i865 IGP (OGL 1.3) in 13.04 and 13.10, mesa/unity_support_test is incorrect

When I log into a desktop session in Ubuntu 13.04 and 13.10 (both the Live CD and a fresh install), the top panel and launcher both seem to completely fail to load.

When viewing console output via one of the virtual terminals, I can see that compiz is failing to load the OpenGL plugin.

compiz (core) - Error: Plugin 'opengl' not loaded.

Right-clicking on the wallpaper still brings up the right-click menu as expected, but performance is extremely slow.

I am using an Intel i865 IGP (82865G), which supports the OpenGL 1.3 standard. This appears to be where the bug lies.

unity_support_test gives an incorrect report of the IGP, stating that it supports OpenGL 1.4. This was not the case with Ubuntu 12.10, the last Ubuntu release where Unity worked on this computer.

Ubuntu 12.10's unity_support_test yields the correct test result (GL version is 1.4+: no), while 13.04 and 13.10's yields an incorrect test result (GL version is 1.4+: yes).

Could potentially be an issue with the version of mesa included with 13.04 and 13.10.

Ubuntu Version: Ubuntu 13.04, 13.10 i386
What is expected to happen: Unity loads, unity_support_test returns "GL version is 1.4+: no"
What happened instead: Unity does not load, compiz fails to load opengl plugin, unity_support_test returns "GL version is 1.4: yes"

IGP/GPU: Intel Extreme Graphics 2 82865G (i865 chipset)