Finish the c32ncp.c/c32ncp.h to ncpapi.c/ncpapi.h rename.
Update the build files, include directives, dependency tracking, header guard,
README references and file-level comments to use the new ncpapi naming. This
matches the current split where ncpapi contains the ncpXX_YY_* protocol API
wrappers and ncpcall contains the lower-level requester/transport helpers.
No behavior change.
