Add .abi-compliance-history to back-branches.

This file was previously added to v18 by commits a72f7d9 and
93fb76c.  Unlike the v18 version of the file, the back-branch
versions set the original baseline point to the most recent ABI
break documented in the git commit history.  While we'd ordinarily
set it to something just before the .0 release, we're unlikely to
act upon ABI breaks in released minor versions, so it doesn't seem
worth the trouble to construct a comprehensive history.

Discussion: https://postgr.es/m/aPfDOD6F4FaJJd7M%40nathan
Backpatch-through: 13-17

Author: nathan-bossart

.abi-compliance-history

@@ -0,0 +1,30 @@
+# Reference point for ABI compliance checks
+#
+# This file lists commits on the current branch that break ABI compatibility in
+# ways that have been deemed acceptable (e.g., removing an extern function with
+# no third-party uses).  The primary intent of this file is to control the ABI
+# compliance checks on the buildfarm, but it also serves as a central location
+# to document the justification for each.
+#
+# In general, entries should be added reactively after an abi-compliance-check
+# buildfarm failure.  It is important to verify the details of the breakage
+# match expectations, as the first entry listed will become the updated ABI
+# baseline point.
+#
+# Add new entries by adding the output of the following to the top of the file:
+#
+# $ git log --pretty=format:"%H%n#%n# %s%n# %cd%n#%n# <ADD JUSTIFICATION HERE>" $ABIBREAKGITHASH -1 --date=iso
+#
+# Be sure to replace "<ADD JUSTIFICATION HERE>" with details of your change and
+# why it is deemed acceptable.
+
+983b3636259b1502121cbae99d8a2f0d0515d87d
+#
+# Fix re-distributing previously distributed invalidation messages during logical decoding.
+# 2025-06-16 17:35:50 -0700
+#
+# This is the original ABI baseline point for REL_14_STABLE.  The first entry
+# would ordinarily point to something just before the .0 release, but this file
+# was first added in October 2025, and we're unlikely to act upon ABI breaks in
+# released minor versions, so we've chosen to truncate the ABI history to start
+# with the most recent ABI break documented in the git commit history.