Trivial fixes for some IDENTIFICATION comment lines

Hello,

I've noticed that in src/backend/replication/logical/reorderbuffer.c, the
IDENTIFICATION comment line is incorrect:

* IDENTIFICATION
* src/backend/replication/reorderbuffer.c

By using a simple find+grep command I can see this is also the case for the
following files:

$ find src -name \*.c -o -name \*.h | xargs grep -A1 IDENTIFICATION | grep
-v -E 'IDENTIFICATION|--' | grep -v '^\(src/.*\.[ch]\)-\s*\*\s*\1\s*$'

src/include/utils/evtcache.h- * src/backend/utils/cache/evtcache.c
src/backend/utils/cache/relfilenodemap.c- *
src/backend/utils/cache/relfilenode.c
src/backend/utils/adt/version.c- *
src/backend/storage/ipc/dsm_impl.c- * src/backend/storage/ipc/dsm.c
src/backend/replication/logical/reorderbuffer.c- *
src/backend/replication/reorderbuffer.c
src/backend/replication/logical/snapbuild.c- *
src/backend/replication/snapbuild.c
src/backend/replication/logical/logicalfuncs.c- *
src/backend/replication/logicalfuncs.c
src/backend/commands/dropcmds.c- * src/backend/catalog/dropcmds.c

The one wtih version.c is a false positive: there's just an extra blank
line in the comment.

A patch to fix the the above is attached.

Another minor thing is that if there is a convention for the order of
Copyright, NOTES and IDENTIFICATION, then it is not followed strictly.
Compare e.g. reorderbuffer.c vs. snapbuild.c.

--
Alex