vchoi_fork

[svn-r10081] Purpose:  Some Kind of Verification

Description:  The library didn't handle incorrect hardware conversion for datatype.  It simply did
convert to incorrect data if any hardware didn't handle correctly.

Solution:  During configuration, incorrect hardware conversion is detected and some macros are
defined.  Use these macros to decide whether to register hardware conversion in H5T.c.  If no hardware
conversion function is registered for certain pair of datatypes, software conversion function will
be used as the conversion path.  Although slower than hardware conversion, we're more confident
software conversion is accurate.

So in one sentence to describe library's behavior, if some hardware conversion doesn't work well,
software conversion will be used instead.

Platforms tested:  h5committest and fuss.

Misc. update:  some changes to configure's comments.