include: fix IS_ERR on Windows

include: fix IS_ERR on Windows

The "long" type uses 32b on x64 Windows platforms, which means
it's not large enough to store a pointer. intptr_t or uintptr_t
should be used instead.

This change fixes include/err.h, using the right types. There was
a previous patch on this topic but unfortunately it didn't address
all the type casts.

This issue was brought up by the unittest_crush test, which recently
started to fail as the CrushWrapper methods use IS_ERR.

Signed-off-by: Lucian Petrut <lpetrut@cloudbasesolutions.com>