dietlibc cvs unstable

The current dietlibc cvs is currently unstable because I recently
changed a few major things.

My main development platform is AMD64, so that should still work fine
for now.

The main change is: if dietfeatures.h contains WANT_TLS, errno is a now
thread-local variable.  The syscall wrappers for all the platforms need
to be changed for this.

The other change is that I added a C11 threading library.  C11 threading
is only a small subset of pthread, and I'm not much of a threading
expert, so the implementation might still be wrong.  However, the new
threading code exclusively uses Linux 2.6+ primitives and should thus
scale much better than the pthread implementation we have.

I also tried to make dietlibc compile with clang, but that is an uphill
battle and right now does not work.  I think we may be out of luck
unless we tell clang to use GNU as instead of the built-in assembler
which does not understand the macro functionality of GNU as that we use.

Help in any of these areas is greatly appreciated!

Felix