[Oberon] Updated V4 for Linux bootloader

[Bernhard Treutwein]

The latest/current version of V4 Oberon for Linux (1.7.02 from 
SourceForge 
https://sourceforge.net/projects/oberon/files/Oberon%20V4%20for%20GNU_Linux/1.7.02/ dated 
2004) contains a bootstrap loader written in an outdated C version and 
some syntax problems in the start script.

With a lot help of ChatGPT I was able to update the C code so that it 
compiles an runs under a more recent 64bit version (bookworm, i.e. 
oldstable).

see https://github.com/btreut/Oberon4Linux-Bootstrap

All testers and feedback is welcome.