Adjust re_fieldname_match to allow for kind, len.

[jhogg41]

At present code doesn't cope with kinds, lengths and other such parameters to types.

e.g. It will choke on the following:

.. f:subroutine:: test(mystring, mylong)

:p character(len=*) mystring: A string :p character(long) mylong: A long integer

This patch fixes that.