fpspreadsheet: Caching the result of the worksheet's GetLastColIndex and GetLastRowIndex for better writing performance of large ods files (which query these data in the row loop). Has no significant effect, though.

git-svn-id: http://svn.code.sf.net/p/lazarus-ccr/svn@3302 8e941d3f-bd1b-0410-a28a-d453659cc2b4