In the latest release of WinAVR, 20090313, in the file iox128a1.h, there is no prototype for CPU_t. I'm assuming this is where it should be, as in any case the typedef is called at line 2544
#define CPU (*(CPU_t *) 0x0030) /* CPU Registers */
So if you're trying to compile in support for the XMEGA software reset, you might take note of this, as the CPU.CPP register must be set to 0xD8 in order to "enable change of the protected register".
In any case, use this code for a software reset:
Also, it would seem to me that #defines to the effect of CPU_CCP_IOREG 0xD8 and CPU_CCP_SPM 0x9D might be handy.