hdf5_ep

[svn-r10456] Purpose:  New way to do conversion test from floating-points to integers.

Description:  The 6th step of changing conversion test.  This checkin is
only for conversion of special values from floating-points to integers.

Solution:  This test is seperated from regular value conversion.  It reuses
the same function test_conv_int_float() in test/dtypes.c.  The source buffer
of floating-point type is filled up with 8 special values, +/-0, +/-infinity,
+/-QNaN, +/-SNaN.

Also added 3 new conversion exception values H5T_CONV_EXCEPT_PINF, H5T_CONV_EXCEPT_NINF,
H5T_CONV_EXCEPT_NAN, for floating-point special values positive infinity, negative
infinity, and NaN.  These values are for conversion exception callback function defined
through H5Pset_type_conv_cb(). (Remember to update the document!)

Platforms tested: h5committest