Compile fixes committed

[Pavel Roskin]

Hello!

I've committed three compile fixes to the classic GNU GRUB.

1) The "configure" file was generated with Automake 1.7.x macros, but
Automake 1.9.4 is actually used for the makefiles.  I've regenerated
"configure".  Ideally, the current version of Autoconf and Automake
should be used for the next release.

2) There were two variables declared both static and external in the
network code.  I've removed the external declarations.  One of the
variables turned out to be write-only, so I've removed it completely.

3) Two network drivers tried to make a non-volatile variable volatile by
a cast.

I believe it's very important to keep GNU GRUB is a working condition.

-- 
Regards,
Pavel Roskin