emerge kde # or whatever depends to svgalib
# wait until the source in unpacked
# change the screen, e.g. <Alt>+<F2>
cd /var/tmp/portage/svgalib-1.9.17-r3/work/svgalib-1.9.17/kernel/svgalib_helper/
vi kernel26compat.h
# and finally delete the offending type definition:
# 1. kernel26compat.h:17: redefinition of `irqreturn_t'
# 2. /usr/src/linux/include/linux/interrupt.h:16: `irqreturn_t' previously declared here
# <dd> at "typedef void irqreturn_t;"