pidgin/pidgin

Make our windows builds usable from meson.
release-2.x.y
2021-04-19, Gary Kramlich
2ff89178eb3d
Make our windows builds usable from meson.

This creates our pkg-config files on windows as well as fixes an include in
pidgin.h which can cause some issues.

This isn't usable as is, as you need a machine-file and a pkg-config wrapper
to make this all work, but that will be updated in the win32-dev.7z file thats
on data.imfreedom.org.

Testing Done:
Compiled guifications2 (which now uses meson) on windows and verified it works.

Reviewed at https://reviews.imfreedom.org/r/615/
For information on writing a plugin for Purple, Pidgin or Finch, go
http://developer.pidgin.im and click on API. From there, see the
HOWTOs in the "Related Pages" section.
You can also generate this documentation locally by installing
doxygen and graphviz dot, then running "make docs" in the
source tree. The documentation will be in the docs/html directory.