I know exactly where it is. That is in /usr/share/arduino/hardware/arduino/cores/arduino/wiring.h
There is a define that causes grief. I think it is around line 79 in that file you will find a "#define round" macro. You need to comment it out like this:
// #define round(x) ((x)>=0?(long)((x)+0.5):(long)((x)-0.5))
It tries to replace the declaration of round in the math.h header file (line 426) and causes that compiler error.
Edit: Oops! I didn't know exactly where it is in YOUR install.
This is due to the upgrades I suggested back in August. The avr-gcc-1.7.1 delay.h file was missing the "#include <math.h>", so I would get a "no declaration for fabs and ceil" error. But when I added that include file, then I got the error you are getting now. The Ubuntu repository has both my bug fixes. That version of Arduino obviously does not.