xlsbiff5 and xlsbiff8 must be descendants of a general biff class as many unsupported tags are common for both formats, some of them even common with biff2.
Added a list of unsupported tags to xlsbiff5 (IFDEFed) to easilly catch tags that must be supported like RK and MULRK which prevent it for load completly many xls files. xlsbiff8 must support them also.
git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@795 8e941d3f-bd1b-0410-a28a-d453659cc2b4
0cae800f3e