[kaffe] removing gc and threads convenience libraries

[Dalibor Topic]

With the gc-refs work from yesterday, it's possible now to remove the gc 
  convenience library from the build (and I have a patch to do it 
sitting on my disk).

But in order to work for boehm-gc, unix-pthreads need to be compiled 
with some specific flags, so I'd like to do it in one go, too,
and eliminate the need for the build system to crawl in the 
kaffe/kaffevm/system directories at all, making it all a bit faster.[1]

Since Automake does not like it when an object file with the same name 
can be generated from two different paths, and we have two files with 
the same name in unix-pthreads and unix-jthreads (and the other thread 
implementations) I've looked at the signal.c and syscalls.c files.

We can purge the syscalls interface from the threading subsystem by 
removing its last users, findInJar.c and jar.c. I'll use libzzlib to 
replace those files, and then remove the syscalls.c code from threading 
implementation.

Unifying the signal.c files across threading implementations also seems
quite easy, so that'll be next.

After that's done, I'll be able to eliminate the need to build the gc 
and threading libraries separately as convenience libs, and move on to 
eliminating the convenience libs used for the engines.

cheers,
dalibor topic

[1] Faster builds are better builds.