pidgin/pidgin

Add a propagation signal for populate-menu to PurpleContactManager

Testing Done:
Ran the unit tests under valgrind.

Reviewed at https://reviews.imfreedom.org/r/2838/
syntax: glob
.*.swp
.DS_Store
.flatpak-builder
*.pyc
*~
\#*\#
syntax: regexp
^build(.+)?\/
win32-install-dir(\.release)?
po\/pidgin3\.pot$
^subprojects\/.+\/