Remove unused files from repository

[ceeac]

This patch removes display/text_pixel.c and utils/omzet2.c. Both files are old and unused by now so it does not make sense keeping them. I also removed the Makefile rules for building *.c files since there are no more *.c files that might need these rules.

[prissi]

Lots of nostalgia for the hand optimised assembler 15 years ago ... indeed, it can go. I just leave the *.c rule in the makefile, should we come across some third party stuff that will need it sometimes. Or could they do any harm?

On a different note, the allegro backend is also broken for current allegro versions ...

[ceeac]

I just leave the *.c rule in the makefile, should we come across some third party stuff that will need it sometimes. Or could they do any harm?

I think not - but if they are removed now, the commit could always be reverted when the rules are required again.

On a different note, the allegro backend is also broken for current allegro versions

I have no problems compiling with v4.4.3.1 - for v5.x this is of course another matter since the API is different. So adding support for Allegro 5 would require adding yet another simsys_*.cc backend.

[prissi]

Hmm, I failed to compile 4.4.3.1 with MSVC ...