Patch: update 4.3 changes for gcj

[Paolo Bonzini]

I think the notice on "jar" in prerequisites.html should be changed from

jar, or InfoZIP (zip and unzip)
     Necessary to build libgcj, the GCJ runtime

to something like this:

InfoZIP (zip and unzip)
     Needed to use the implementation of "jar" that is included in 
libgcj.  Not necessary if a standalone "jar" program is already installed.

Actually, the fact that "jar" is not needed anymore to build libgcj 
(right?), and that many .jar files are distributed together with libgcj, 
could give motivation to finally include Classpath's jar implementation 
in libgcj (both as source and as a .jar file) instead of my script. 
Even though I love that script. :-P

Paolo