5.7.1 Process .sg to create %dt hash (throw away XSD output)

xsd2sg.pl first processes the .sg files to XSD. As a side effect it populates %dt multidimentsional hash

  $dt{'element'}{elemname}[array-of-sublemens-and-attrs]
  $dt{'attribute'}{attrname} = "";
  $dt{'complexType'}{typename}[array-of-sublemens-and-attrs]
  $dt{'group'}{groupname}[array-of-sublemens-and-attrs]
  $dt{'attributeGroup'}{agname}[array-of-attrs]

Where the array-of-subelems-and-attrs can contain tag or reference to fundamental or derived type, e.g.

  "tag$sa:Assertion$min$max"
  "ref$xs:anyURI$"
  "ref$sa:Assertion$"
  "base$$0$1$base-type"
  "enum$n1$n2$n3$n4$n5"
  "any$$min$max$pc$ns"
  "anyAttribute$$min$1"
  "_d$$0$1$simplecontent"