v0.2.1-alpha

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

Code changes:
+ Fix autotopic.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.
+ In some debugging, switch from `purple_account_get_name_for_display`
to `purple_account_get_username` for compatibility with the older
version of the pidgin in my Linux development environment.