Remove cpp_std overrides and add support for VS 2019
This MR depends on gst-plugins-good!182 (merged)
recipes: Don't set cpp_std anymore, it's set per-plugin See: https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/merge_requests/301 https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/merge_requests/182
cerbero: Add support for building with VS2019
meson.recipe: Add support for VS2019 Bumping to 0.50.1 would also work, but it's too close to the 1.16 release to do that.
Closes #126 (closed)