r313305 libevent2 problem and workaround NEED FIXING...

[Jeffrey Bouquet]

A huge six-day fix of seamonkey breakage on 11-CURRENT of april 2016, upgraded
finally last night to pkg 12-CURRENT feb 2017 working and etc by base.txz 
overwrite etc...
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I've many many hours to restore the desktop to full how-it-was-before, but as it
is working, now, a wholesale 3xxx reinstall of ports by pkg (which had to
occur OUT OF Xorg for stall issues... and lack of granularity in the
use of "pkg upgrade"  (ie thirty-by-thirty) or lack of code in
"pkg install" (terse deinstalls necc. where reinstalls were needed)
as of this date....
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Mostly fixed as I write from the fixed system, but the only reason I am using seamonkey
now, and also fixed firefox, just then, is the series of commands... which I expect to
maybe re-break when v12 upgrades _4 seamonkey to _5 which broke (segfaults) here
from ports the port... but in the meantime
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cp -iv /[backup mount}/usr/local/lib/libevent-2.0.so.5.10 /usr/local/lib/compat/libevent-2.0.so.5
cp -iv /usr/local/lib/compat/libevent-2.0.so.5 /usr/ports/www/seamonkey/libevent-2.0.so.5-NECC-FOR-SEAMONKEY
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backup restored a newly overnight broken seamonkey AND firefox, the former not as of a day or
so from ports being able to run.
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This is quite the showstopper here... almost forced a reinstall of 2004-2017 ( this desktop)
to a 2016-STABLE v11 new disk.... which I may have to revert to if seamonkey breaks again or
the next iteration of libevent/seamonkey/firefox does not fix up with CLI such as this time.
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Out of time for a PR or bug report offically, and hope to gain more
pressing urgency to this problem than might be attained, that way... out of time also.
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Thanks for reading, and thanks for putting up with interim list messages in the last few
days which still had a bit of almost PBKAC combined with lack of documentation combined with
newbie-ness here which had yet to resolve... 
and thanks for the forum post(s) which helped resolve the seemingly-lost-cause issue of the
v11-CURRENT upgrade to  v12-CURRENT which appears to have worked today vs several
days ago, IF seamonkey continues to be fixable locally.
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J. Bouquet