debugging guile runtime

[rixed]

Hello !

I'm still annoyed by the runtime bugs related to ports/threads at work,
so I can devote some time to work on it.

So far, the pending problems are, in order of importance for me :

#1 ports are not thread safe (and any other thread safety issues) ;
#2 fork may freeze in some occurrence ;
#3 the use of select prevent the extended app to open more than 1024
   files ;
#4 fork does not close all open files.
#5 new syntax definitions are not loaded by compiler

for #3, I already have a patch (that I sent here some months ago but was
neither rejected nor accepted as far as I know), for #5 there are
various easy workarounds, but for other bugs I am still stuck.  So, I'm
willing to work on those if someone who's already familiar with the
runtime can give some guidance.