+ implemented exception handling via throw()
+ added IDF ownership compliance rules
+ added support for IDFv2 since this ancient format is still in use
+ cleaned up code to allow easy integration into a DLL; no
  exceptions shall be thrown outside the library.
+ fixed some IDF compliance bugs
+ added various options to idf2vrml:
  - flag '-d' to suppress default missing outline substitution
  - flag '-z' to suppress default zero-height substitution
  - flag '-m' to enable printout of RefDes to OBJECT mapping for diagnostics