Remove the 2026 Mario Fetka copyright line from ipx.asm.
The file contains the split-out IPX and xmemmove assembly glue from the original
Martin Stover kern.asm code, without new authorship-bearing changes.
No behavior change.
Split the Open Watcom assembly glue into separate IPX and NCP requester
modules.
Keep the IPX socket and far-memory helper entry points in ipx.asm and move the
INT 21h Net_Call plus Client32 requester entry points into ncpcall.asm. Split
the former kern.h declarations accordingly into ipx.h and ncpcall.h, and update
net.h and the Open Watcom build to use the new headers and object files.
This matches the current source layout where ncpcall.c owns the low-level NCP
transport helpers and ncpapi.c owns the ncpXX_YY_* protocol API wrappers.
No behavior change.
