Version v0.2.1-alpha

Functional changes:
+ Provide linux `.so` plugin file

Code changes:
+ Fix akaplugin.c so that it includes <libpurple/foo.h> for the
libpurple include files, so that it can compile under either Linux or
Windows,.
+ First, rough, version of a `Makefile` that will work under either
Linux or Cygwin - or at least, my installations of each.