wchar_t and stddef.h mess

[sezero]

Doing #include <stddef.h> without any -mcrt args or with -mcrt=libnix
includes /opt/m68k-amigaos/lib/gcc-lib/m68k-amigaos/2.95.4/include/stddef.h
i.e. the gcc-provided header (not the libnix one), which defines whar_t
as unsigned int (see gcc/config/m68k/amigaos.h for WCHAR_TYPE definition.)
However, libnix headers (apparently copied from ixemul) defines it as int,
i.e. signed, in machine/ansi.h.

Because of this, including stddef.h followed by stdlib.h results in an
error: (if the include order is flipped, no errors, though.)

$ /opt/m68k-amigaos/bin/m68k-amigaos-gcc -c 1.c
In file included from /opt/m68k-amigaos/lib/gcc-lib/m68k-amigaos/2.95.4/../../../../m68k-amigaos/sys-include/stdlib.h:40,
                 from 1.c:2:
/opt/m68k-amigaos/lib/gcc-lib/m68k-amigaos/2.95.4/../../../../m68k-amigaos/sys-include/machine/ansi.h:51: warning: `_BSD_PTRDIFF_T_' redefined
/opt/m68k-amigaos/lib/gcc-lib/m68k-amigaos/2.95.4/include/stddef.h:112: warning: this is the location of the previous definition
/opt/m68k-amigaos/lib/gcc-lib/m68k-amigaos/2.95.4/../../../../m68k-amigaos/sys-include/machine/ansi.h:52: warning: `_BSD_SIZE_T_' redefined
/opt/m68k-amigaos/lib/gcc-lib/m68k-amigaos/2.95.4/include/stddef.h:159: warning: this is the location of the previous definition
In file included from /opt/m68k-amigaos/lib/gcc-lib/m68k-amigaos/2.95.4/../../../../m68k-amigaos/sys-include/stdlib.h:43,
                 from 1.c:2:
/opt/m68k-amigaos/lib/gcc-lib/m68k-amigaos/2.95.4/../../../../m68k-amigaos/sys-include/sys/types.h:110: warning: redefinition of `size_t'
/opt/m68k-amigaos/lib/gcc-lib/m68k-amigaos/2.95.4/include/stddef.h:170: warning: `size_t' previously declared here
In file included from 1.c:2:
/opt/m68k-amigaos/lib/gcc-lib/m68k-amigaos/2.95.4/../../../../m68k-amigaos/sys-include/stdlib.h:52: conflicting types for `wchar_t'
/opt/m68k-amigaos/lib/gcc-lib/m68k-amigaos/2.95.4/include/stddef.h:255: previous declaration of `wchar_t'

Is there actually a reason why gcc defines whar_t as unsigned int?
The gcc-6 fork of @bebbo seems to define it as unsigned int, too.
However, amigaos4 gcc-4.2 defines it as long int, so does morphos
gcc-4.4 and aros.

I guess machine/ansi.h of libnix (ixemul) needs changing to follow
gcc for this?