Added symbolic links 'libarch','libadt','libipc' into libc/include,
so that it can be easily used from anywhere.
Renamed thread_main to thread_main.
Allowed MIPS to compile with -O0.
Added non-preemptible threads support (not yet secured by futexes).
Added simple way to hold Thread Local Storage. Support for compiler
will be added later.
This update breaks IA64 uspace.
There is some forgotten spinlock_lock() in futexes, amd64 gets locked
in the secod uspace thread probably with preemption disabled.
