Fixed compilation error on Windows (MSVC) in XmlFormatter.h

ctime_r() function used to format date in output Xml is not available on Windows. The fix allows the date to be formatted both on Windows and on *nix.
Fixed compilation warnings

Fixed a number of compilation warnings: 
- comparison between size_t and unsigned
- implicit cast from int to bool
Merge pull request #86 from kindkaktus/master

Fixed compilation error on Windows (MSVC) in XmlFormatter.h