pidgin/pidgin

Prepare for the 2.14.8 release
release-2.x.y v2.14.8
2021-10-14, Gary Kramlich
5076f03ecaaa
Prepare for the 2.14.8 release

Testing Done:
Ran `make distcheck`

Reviewed at https://reviews.imfreedom.org/r/1043/
installed_m4=purple.m4
EXTRA_DIST=$(installed_m4)
m4datadir=$(datadir)/aclocal
m4data_DATA=$(installed_m4)