- fix setting the REAL_GCC_VERSION if no snapdate was given (i.e. we're using a svn co of the branch).
  sjhill, please verify that this still works for you!

- move setting of determination whether we use a full kernel vs. sanitized headers into the generic part

- nil CXX if there isn't one

- improve the -clean target

- put the full kernel's sources into build_/, install them into toolchain_build_. Saves quite some disk-space on the compile-host.
- Avoid overriding the linux26 target's rules if the kernel headers's and the target's kernel are the same. Avoids a warning.

  for both host and target build. Thanks to Ulrich Hecht.

  own dirs. Thanks to Ulrich Hecht.

- ignores TARGET_CC (overwritten in Makefile)
- ignores TARGET_CFLAGS
- is hardcoded to use the i386 target