Port the updates from 2.14.2 and the upcoming 2.14.3 to 3.0.0

* Use the unicode version of the System and UserInfo plugins to fix
non-english languages in the Windows installer.
* Update the installer to use the inetc plugin so that https downloads will
work. This became necessary because Sourceforge now redirects http to
https.
* Standardize everything in pidgin/win32/winpidgin.c to use `wprintf`.

Testing Done:
Compiled and ran on windows 10.

Reviewed at https://reviews.imfreedom.org/r/595/