Fix VPATH build of RQUOTA support. Some rpcgen derive #include "..." paths from the infile argument. This will be off for VPATH builds, as the generated rquota_xdr.c code will look in $(srcdir), but we'll generate the rquota.h file in $(builddir). Play safe and copy rquota.x to $(builddir) first. This fixes the build on openSUSE 11.1.

#ifndef UNLINK_OLD_FILES_H
#define UNLINK_OLD_FILES_H

/* Unlink all files from directory beginning with given prefix and having
   ctime older than min_time. Returns -1 if there were some errors. */
int unlink_old_files(const char *dir, const char *prefix, time_t min_time);

#endif