MSVC patch: make OCTAVE_HDF5_DLL test work with compiler optimization turned on

[Michael Goffioul]

Index: aclocal.m4
===================================================================
RCS file: /cvs/octave/aclocal.m4,v
retrieving revision 1.104
diff -c -r1.104 aclocal.m4
*** aclocal.m4  7 Feb 2007 09:01:24 -0000       1.104
--- aclocal.m4  13 Jun 2007 20:14:40 -0000
***************
*** 994,1004 ****
 dnl
 AC_DEFUN([OCTAVE_HDF5_DLL], [
   AC_CACHE_CHECK([if _HDF5USEDLL_ needs to be defined],octave_cv_hdf5_dll, [
!     AC_TRY_LINK([#include <hdf5.h>], [hid_t x = H5T_NATIVE_DOUBLE;],
       octave_cv_hdf5_dll=no, [
       CFLAGS_old=$CFLAGS
       CFLAGS="$CFLAGS -DWIN32 -D_HDF5USEDLL_"
!       AC_TRY_LINK([#include <hdf5.h>], [hid_t x = H5T_NATIVE_DOUBLE;],
         octave_cv_hdf5_dll=yes,
       octave_cv_hdf5_dll=no)
       CFLAGS=$CFLAGS_old])])
--- 994,1004 ----
 dnl
 AC_DEFUN([OCTAVE_HDF5_DLL], [
   AC_CACHE_CHECK([if _HDF5USEDLL_ needs to be defined],octave_cv_hdf5_dll, [
!     AC_TRY_LINK([#include <hdf5.h>], [hid_t x = H5T_NATIVE_DOUBLE; return x],
       octave_cv_hdf5_dll=no, [
       CFLAGS_old=$CFLAGS
       CFLAGS="$CFLAGS -DWIN32 -D_HDF5USEDLL_"
!       AC_TRY_LINK([#include <hdf5.h>], [hid_t x = H5T_NATIVE_DOUBLE;
return x],
         octave_cv_hdf5_dll=yes,
       octave_cv_hdf5_dll=no)
       CFLAGS=$CFLAGS_old])])