1. Added 64 bit Linux  version of plugin.
2. Added makefile to compile both 32 & 64 bit versions of plugin on Linux
3. Added directory to placeholder for x-plane SDK

Signed-off-by: Yuri Ingultsov <yuri@softlab.in.ua>
Merge pull request #2 from softlab/master

1. Added 64 bit Linux  version of plugin.