pidgin/pidgin

Switch join_paths and + to /.

2020-09-16, Elliott Sales de Andrade
c0ea70247280
Switch join_paths and + to /.

Testing Done:
Ran `ninja install`, though didn't actually check the results.

Reviewed at https://reviews.imfreedom.org/r/121/
libpurple/data/purple-url-handler.desktop.in
libpurple/protocols/null/nullprpl.c
pidgin/data/im.pidgin.Pidgin.desktop.in
sub/libpurple/data/purple-url-handler.desktop.in
sub/libpurple/protocols/null/nullprpl.c
sub/pidgin/data/im.pidgin.Pidgin.desktop.in