AcDbDatabase::restoreForwardingXrefSymbols() Function

The restoreForwardingXrefSymbols() function restores the xref back to a valid, attached state. Not only does it restore the original resolved symbols, but it also seeks out newly added symbols and resolves them as well. The restoreForwardingXrefSymbols() function cannot handle newly added, nested xref block table records unless they already exist and are resolved in the host drawing.