Log Message:
Update gnustep-base to 1.6.0.

Noteworthy changes in version `1.6.0'
=====================================

   * More MinGW support

   * New MacOSX compatible methods.

   * The Base Additions library compiles on native OSX.

   * autogsdoc produces better, cleaner docs.

   * Built-in garbage collecting classes.

   * Any many many bug fixes and minor improvements.