gcc-3.0 or newer, but I hope it's OK)

This is done to avoid clashes with gcc-3.3 which has built-in logarithms :)

BTW, where do you exactly set the new buffer sizes?

Also, removed the `if (s)' test, because I believe that as the whole
socket interface doesn't accent NULL pointers, sk_reallocate() shouldn't
be the only exception.

Finally, I found the bug reported by Andreas Steinmetz. FIXED.