GitLab

Our previous include file only supplied a very limited set of
wrapper redefinitions for platforms that define __APPLE__ (i.e.
Mac OS). In particular, some needed big endian conversions were
missing, causing "symbol(s) not found" errors when linking.

Instead of patching the existing file, let's do away with it
completely and replace it by something more sophisticated.
The portable_endian.h used is in the public domain, and was
taken from https://gist.github.com/panzi/6856583

Signed-off-by: Bernhard Nortmann <bernhard.nortmann@web.de>