gplugin/gplugin

Add the ability to disable the native plugin loader

2020-09-14, Gary Kramlich
04f8758f9a72
Add the ability to disable the native plugin loader

Add support for the ability to disable the native plugin loader. This is primarily a debug tool right now. Fixes GPLUGIN-103

Testing Done:
Built and ran the unit tests locally.

Reviewed at https://reviews.imfreedom.org/r/110/
There are a few notes about building on OSX.
First off, building has *ONLY* been tested against homebrew. If you want to
support fink or macports, please let me know and I will merge your pull
request.
Currently there is no known way to build the Perl loader on MacOS. So you
**MUST** run meson with `-Dperl5=false`.
## Lua
For the Lua loader to work, you need to install `lgi` from luarocks either
systemwide or to a virtual environment created by LuaDist, vert, or something
along those lines, then you just need to run `luarocks install lgi`.
## Python3
If you're using homebrew, you need to install `pygobject3`.