dispatch.c requires stdio.h (and stdarg.h), however, currently
dispatch.c implicitly relys on rpc/xdr.h to include stdio.h.
If rpc/xdr.h unxpectedly does not include stdio.h, the compilation
of dispatch.c fails.
This can happen, for example, when portablexdr is installed
under /usr/local; because portablexdr's rpc/xdr.h does not
include stdio.h and gcc looks up it not /usr/include/rpc/xdr.h.
Note that stdarg.h is also included according to man va_start,
although stdio.h seems including it anyway.
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