rpl_gethostname undefined on MinGW system when compiling Octave

[John W. Eaton]

I'm getting an error about rpl_gethostname undefined when compiling 
Octave for MinGW.  HAVE_GETHOSTNAME is 1, so the AC_LIBOBJ macro from 
the module/gethostname file is not used, but unistd.in.h is checking 
GNULIB_GETHOSTNAME, which is also defined to 1.  So the macros there are 
expanded and I get the undefined symbol.  Since the module indicator 
variable is expanded after the snippet from module/gethostname, the 
simple fix of switching the test from $HAVE_GETHOSTNAME = 0 to 
$GNULIB_HOSTNAME = 1 doesn't work.

It's not clear to me what the correct fix should be.  Any help would be 
much appreciated.

jwe