pidgin/pidgin

Update the date in COPYRIGHT as it was a few years behind
release-2.x.y
7 weeks ago, Gary Kramlich
21a56db5f998
Update the date in COPYRIGHT as it was a few years behind

Testing Done:
None

Reviewed at https://reviews.imfreedom.org/r/3007/
installed_m4=purple.m4
EXTRA_DIST=$(installed_m4)
m4datadir=$(datadir)/aclocal
m4data_DATA=$(installed_m4)