Adds a PACKAGECONFIG option to use libsoup2 instead of libsoup3.
Including libsoup2 and libsoup3 in the same process can cause strange
runtime failures, and the latest release of each major version will
cause the process to exit if both are detected on startup.
The default is changed from libsoup3 back to libsoup2 to follow
webkitgtk.
Signed-off-by: Joshua Watt <JPEWhacker@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
