Use standard shared library versioning.

Index: gettext-tools/src/Makefile.in
--- gettext-tools/src/Makefile.in.orig
+++ gettext-tools/src/Makefile.in
@@ -3965,7 +3965,7 @@ cldr_plurals_LDADD = libgettextsrc.la $(LDADD)
 # Need @LTLIBINTL@ because many source files use gettext().
 # Need @LTLIBICONV@ because po-charset.c, po-lex.c, msgl-iconv.c, write-po.c
 # use iconv().
-libgettextsrc_la_LDFLAGS = -release @VERSION@ \
+libgettextsrc_la_LDFLAGS = \
 	../gnulib-lib/libgettextlib.la $(LTLIBUNISTRING) \
 	$(LT_LIBTEXTSTYLE) @LTLIBINTL@ @LTLIBICONV@ -lc -no-undefined \
 	$(am__append_3) $(am__append_5) $(am__append_7)