fpspreadsheet: Remove reading code for RK and MULTRK records from xlsbiff5 and xlsbiff8, use the xlsbiff8 versions in xlscommon. --> Formatting of RK and MULRK works now for biff5 as well.

git-svn-id: http://svn.code.sf.net/p/lazarus-ccr/svn@3042 8e941d3f-bd1b-0410-a28a-d453659cc2b4