Default to Unicode build for Alien::wxWidgets?

[Mattia Barbon]

  Hi,
while testing for a bug report, I noticed that by default 
Alien::wxWidgets builds wxWidgets in non-Unicode (a.k.a. ANSI) mode. The 
only platforms where wxWidgets does not work in Unicode mode are Windows 
95, 98, ME and Unix platforms using Motif.

  I think it will be safe to have another configuration option (just 
before the one about OpenGL) defaulting to 'yes'.

  What do you think?

Regards,
Mattia