Build your own IDE with removed lines:
https://github.com/arduino/Arduino/blob/ide-1.5.x/app/src/processing/app/debug/Compiler.java
if (prefs.get("build.mcu").equals("atmega2560"))
optRelax = ",--relax";
This solved this problem:
c:/users/gregor/desktop/arduino/arduino-1.5.4-r2-windows/arduino-1.5.4/hardware/tools/avr/bin/../lib/gcc/avr/4.3.2/../../../../avr/lib/avr6/crtm2560.o: In function `__vector_default':
(.vectors+0x28): relocation truncated to fit: R_AVR_13_PCREL against symbol `__vector_10' defined in .text section in c:/users/gregor/desktop/arduino/arduino-1.5.4-r2-windows/arduino-1.5.4/hardware/tools/avr/bin/../lib/gcc/avr/4.3.2/../../../../avr/lib/avr6/crtm2560.o
But the best solution is:
Add to global area:
#include <avr/pgmspace.h>
const char pad[500] PROGMEM = { 0 };
and add this to the fist line of setup:
pad[0];
See:
http://forum.arduino.cc//index.php?topic=140108.msg1440380#msg1440380