fix compilation on linux and generate iso

[daniel-k]

mkdir -p $(DESTDIR)$(tooldir)/lib${MULTISUBDIR}
mkdir -p ${DESTDIR}${tooldir}/include/sys

was needed because at the time of execution, the destination directory didn't exist yet. I have no idea why this differs on Mac OS but it fixes linking issues not finding 'link.ld'.

Secondly I had to disable large file support because of linker errors not finding symbols __swrite64 and __sseek64 while linking examples. Apparently these functions are defined in newlib/libc/stdio64/, but this directory won't be compiled neither on my linux machine nor on Mac OS. Again, I have no clue why this works as is on Mac OS.

Both fixes don't seem nice enough because they require manual merging when upgrading newlib again and only fight the symptoms, so maybe someone has a better clue on how to solve this.

[daniel-k]

So I also tried to boot eduOS in Virtualbox. Therefore I had to create an ISO image that in the end can be booted on any x86 computer. It uses GRUB2 to boot eduos. Still there are 2 things needing review:

1. The Makefile in tools now requires the program genisoimage which might not be available everywhere and, more importantly, is not essential for build eduos, yet leads to an unseccessful build.
2. The magic file eltorito.img has been built according to this [1] guide. I'm not entirely sure if there are any licensing issues.

[1] http://forum.osdev.org/viewtopic.php?p=231379#p231379