fpspreadsheet: Improved detection of space separators in date/time formats. Generally valid, no modification of xmlread required. Side-effect: leading spaces of xml elements have to be skipped manually

git-svn-id: http://svn.code.sf.net/p/lazarus-ccr/svn@3122 8e941d3f-bd1b-0410-a28a-d453659cc2b4