Moved xdr_control() function from static inline in xdr.h in to a
new xdr.c file which was added to the libspl build. Additionally,
I have removed the 'xdr_bytesrec' typedef which shares the same
name as the struct. This is what Solaris does, but it's just asking
for trouble. It has been replaced with an 'xdr_bytesrec_t' typedef.
Brian Behlendorf