Add file_ops.c to GETTEXT_FILES in nls.mk.

Since file_ops.c contains translatable strings, it should have been listed
in GETTEXT_FILES.

src/bin/pg_rewind/nls.mk

 # src/bin/pg_rewind/nls.mk
 CATALOG_NAME     = pg_rewind
 AVAIL_LANGUAGES  =
-GETTEXT_FILES    = copy_fetch.c datapagemap.c fetch.c filemap.c libpq_fetch.c logging.c parsexlog.c pg_rewind.c timeline.c ../../common/fe_memutils.c ../../common/restricted_token.c ../../../src/backend/access/transam/xlogreader.c
+GETTEXT_FILES    = copy_fetch.c datapagemap.c fetch.c file_ops.c filemap.c libpq_fetch.c logging.c parsexlog.c pg_rewind.c timeline.c ../../common/fe_memutils.c ../../common/restricted_token.c ../../../src/backend/access/transam/xlogreader.c
 
 GETTEXT_TRIGGERS = pg_log:2 pg_fatal report_invalid_record:2
 GETTEXT_FLAGS    = pg_log:2:c-format \