Progress on IDL import:

umbrello/codeimport/idlimport.{h,cpp}
- New function skipStructure skips to the end of a struct/union/
  valuetype/interface declaration.
- New function isValidScopedName returns true if the argument conforms
  to IDL syntax for scoped names.
- For processing unions add members m_isUnionDefault of type bool and
  m_unionCases of type QStringList.

umbrello/codeimport/idlimport.cpp
- In function fillSource remove compressing of sequence or bounded
  string into single lexeme.
- In function parseStmt,
  - extend documentation;
  - make local `keyword' non const;
  - on setting stereotypes use prefix "idl" in lieu of "CORBA" for
    compatibility with IDL4;
  - start fleshing out union handling;
  - on handling "typedef" start fleshing out sequence and bounded
    string.

CCBUG: 81301