Move assert implementation to .c file

[agkaminski]

To avoid including stdio.h and stdlib.h in assert.h

[pawelpisarczyk]

Alek, Marek - what are the next steps? What should we do with this issue?

[nalajcie]

You need to assign someone to this task and let him resolve the issue :)

[agkaminski]

This isn't a high priority matter. All this is about is 100% compliance with C and POSIX. It's an issue, so we won't forget about this.