OLPC plan9 kernel Changes

Following files are added to /sys/src/9/pc/ which add EGA emulation on top of OLPC linear frame buffer.

font_sun12x22.h
lfbgeometry.h
lfbega.c
olpc-egainit.c
olpc-egalib.c
olpc-ega.h

Following files are modified :

l.s - Here we need to make a new 4 MB page table entry for mapping OLPC’s linear framebuffer. Also instead of calling main, olpc_display_init is called which prints Plan9 on screen using EGA emulation code. After that HLT is called so that machine won’t reboot.

mkfile - Added entries for new EGA code.