for Mac OS X and add it to the installation Disk Image.


Build-tools/Do-pkg:
   - added code to build the StartupItem PKG along with the MySQL PKG and
     add it to the resulting Disk Image (can be skipped with --skip-si)
   - lots of cleanups (use more builtin Perl functions instead of 
     subprocesses, enable a full dry run without errors)
support-files/MacOSX/StartupItem.Info.plist:
   - removed IFPkgFlagOverwritePermissions and IFPkgFlagUseUserMask