Time format can be specified
Fixed an unsigned/signed mismatch warning with GCC
Minor comments tweaks for doxygen generated documentation.
Made some patches on top of ixe013's changes to support a time format string.  These include:
- Fix compile failures and warnings when LOGOG_UNICODE is enabled
- Fix a warning when compiled in 64-bit mode
- Increase max lengths of time and date format and output strings
Merge branch 'ixe013-set-time-format'