During XML import formulas of defined names and conditional formatting
were remembered as regular svString tokens that then later were
retrieved without quotes for compilation. This didn't go along with the
new ScRangeData::CompileUnresolvedXML() that recreates the formula
string from an already tokenized form of the formula.

Introduced FormulaToken::AddStringXML() with ocStringXML to sort those
out and removed the IsImportingXML() hack from
FormulaCompiler::AppendString(), the ocStringXML case is handled in
FormulaCompiler::CreateStringFromToken().