number of user GDT descriptors specified as configure option
GDT entries information getting functions
implemented protected mode interface according to vbe 3.0

it turns out protected mode is not well supported in hardware
further search showed VBE/AF is not supported as well
32-bit protected mode according to vbe 2.0 should support only bank
switching, while linear frame buffer is probably better way to go
vbe 3 pmi commented parts cleared
prep for graphical mode introduced at bootup
testing VBE PMI
test of VESA Bios Extension real mode interface

succesfull
realmode interface in c function using inline assembler