Fix another portability issue from commit 758ce9b77.

Tom Lane <tgl@sss.pgh.pa.us>

Commit: ce4887bd025b95c7b455fefd817a418844c6aad3
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: 2018-09-26T23:03:40Z
Releases: 12.0
Fix another portability issue from commit 758ce9b77.

strerror.c now requires strlcpy() in some cases, and a couple of the
ecpg libraries did not have that at hand.  Pull it in from src/port/
following the usual recipe.  Per buildfarm.

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