Some more fixes to make release happen

[Ladislav Michl]

Hi Everyone,

I'd like to point you to the preview2 branch
(https://github.com/3x380V/gnokii/tree/preview2)
with most notable changes:
- build and runtime tested on both Linux and Windows. Thanks to
  Fabrizio Gennari cross-compiling for windows host is now as
  easy as:
  ./configure --host=x86_64-w64-mingw32 && make
  (resulting binaries tested on Bluetooth connected C2-00)
- no more device drivers ifdef hell thanks to plugin architecture
- more global varibles moved to instances, so it should now work
  with more than one phone connected.

common/devices/osxbluetooth.m still needs to be fixed, so if
you have OSX, time and knowledge, you are wellcome :)

MSVC builds still untouched and looking at all that outdated
stuff in Windows/* I'm temped to just remove it if noone cares.
Creating working project should be pretty easy and
straightforward now...

Testing and feedback appreciated.

        ladis