valgrind complaints in pgstat_write_statsfile

Seen in passing when running valgrind against a CVS HEAD build:

> ==28598== Syscall param write(buf) contains uninitialised or unaddressable byte(s)
> ==28598== at 0x1BABC558: write (in /lib/libc-2.3.4.so)
> ==28598== by 0x1BA7165D: (within /lib/libc-2.3.4.so)
> ==28598== by 0x1BA715FE: _IO_do_write (in /lib/libc-2.3.4.so)
> ==28598== by 0x1BA70E61: _IO_file_close_it (in /lib/libc-2.3.4.so)
> ==28598== by 0x1BA67B07: _IO_fclose (in /lib/libc-2.3.4.so)
> ==28598== by 0x819369B: pgstat_write_statsfile (pgstat.c:2275)
> ==28598== by 0x8192A44: PgstatCollectorMain (pgstat.c:1576)
> ==28598== by 0x8192368: PgstatBufferMain (pgstat.c:1398)
> ==28598== by 0x8191656: pgstat_start (pgstat.c:617)
> ==28598== by 0x818EB81: reaper (postmaster.c:2096)
> ==28598== by 0x52BFEFFF: ???
> ==28598== by 0x818CDAA: PostmasterMain (postmaster.c:917)
> ==28598== by 0x81570E4: main (main.c:268)

Anything to be concerned about? I guess that the uninitialized bytes
were actually provided in an earlier write but it's only on close that
they get written out and noticed.

-O