hdf5_ep

[svn-r22145] #Issue 7922 - H5Pset_data_transform had seg fault with some operations like x*-100.
The parser mistaked "-" as substraction.  I fixed it and also fixed another problem
with some special cases like 100-x and 2/x.  This is a merge from the trunk.

Tested on jam, koala, and ostrich.