Added Makefile for use on Windows with MinGW.  Added prebuilt libcampfire.dll
for installation on Windows (with pre-installed Pidgin).
Correctly set function scope for local functions.  Attempt to quiet
strict build warnings.
Remove g_list_free_full() which does not work with older versions of glib (esp.
Windows build).  Remove mixed code and declarations which Windows build
complains about.