lguest: tell git to ignore Documentation/lguest/lguest

This is the example lguest launcher binary.

Signed-off-by: Matt Kraai <kraai@ftbfs.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Documentation/lguest/.gitignore

@@ -0,0 +1 @@
+lguest