I noticed that when compiling mesa with --enable-debug some maps of the sauerbraten game are visually corrupted (missing walls), e.g:
http://img692.imageshack.us/img692/8545/sauercorruption.png
while when compiling without it works fine. This happens especially with "maps->douze". I also get warnings like:

Mesa warning: glDraw[Range]Elements(start 6912, end 8677, count 3642, type 0x1403, indices=0x843c)
	end is out of bounds (max=90)  Element Buffer 11 (size 104640)
	This should probably be fixed in the application.
Mesa warning: glDraw[Range]Elements(start 6912, end 8677, count 3642, type 0x1403, indices=0x843c)
	index=8677 is out of bounds (max=90)  Element Buffer 11 (size 104640)
	Skipping the glDrawRangeElements() call

This is similar to bug #22743 and probably it's a sauerbraten bug, but it's strange that I get different rendering when enabling or disabling the --enable-debug flag.

Tested with master, 7.7 and 7.6 branches, with: 
GL_RENDERER   = Mesa DRI R300 (RV530 71C5) 20090101 x86/MMX/SSE2 TCL