vchoi_fork

[svn-r10402] Purpose: New way to do conversion test between floating-point types.

Description:  The 5th step of changing conversion test.  This checkin is only for conversion
of special values between floating-point types.

Solution: This test is seperated from regular value conversion.  It reuse the same function
test_conv_flt_1() in test/dtypes.c.  The source buffer of floating-point type is filled up
with 8 special values, +/-0, +/-infinity, +/-QNaN, +/-SNaN.

Platforms tested: h5committest, fuss, and modi4.