- moved helper functions from Bootstrap script to logger.pm 


Build-tools/Bootstrap:
   - renamed logfile -> LOGFILE
   - moved functions abort() and run_command() to logger.pm for better
     reusability
Build-tools/Do-pkg:
   - heavily reworked: now make use of the logger.pm helper functions
   - added new options: --dry-run, --log, --mail, --verbose
Build-tools/logger.pm:
   - added functions run_command() and abort() from Bootstrap script for
     better code reusability
support-files/MacOSX/postinstall.sh:
   - made script more robust