Add libsndio.so.${MAJ} symlink and use it as SONAME on linux

This avoids having to rebuild a lot of packages even if the
ABI did not break. cubeb used by firefox currently dlopen's
either libsndio.so.7.1 or libsndio.so, with the major link
this would also avoid having to patch this as long as the
ABI doesn't break without having to ship the libsndio.so
symlink outside of -dev/-devel packages.

configure

@@ -60,8 +60,9 @@ case `uname` in
 		alsa=yes
 		ldadd="-lrt"
 		user=sndiod
-		so_ldflags="-Wl,-soname=libsndio.so.\${MAJ}.\${MIN}"
 		so_link="libsndio.so"
+		so_link_maj="libsndio.so.\${MAJ}"
+		so_ldflags="-Wl,-soname=libsndio.so.\${MAJ}"
 		defs='-D_GNU_SOURCE -DHAVE_SOCK_CLOEXEC -DHAVE_CLOCK_GETTIME'
 		;;
 	NetBSD)
@@ -268,6 +269,7 @@ do
 	-e "s:@ldadd@:$ldadd:" \
 	-e "s:@so@:$so:" \
 	-e "s:@so_link@:$so_link:" \
+	-e "s:@so_link_maj@:$so_link_maj:" \
 	-e "s:@so_ldflags@:$so_ldflags:" \
 	-e "s:@vars@:${vars}:" \
 	-e "s:@precision@:$precision:" \

libsndio/Makefile.in

@@ -49,8 +49,9 @@ MAJ = 7
 MIN = 1
 SO = @so@
 SO_LINK = @so_link@
+SO_LINK_MAJ = @so_link_maj@
 
-all:		${SO} ${SO_LINK}
+all:		${SO} ${SO_LINK} ${SO_LINK_MAJ}
 
 
 install:
@@ -59,7 +60,7 @@ install:
 		mkdir -p ${DESTDIR}${MAN3_DIR}
 		mkdir -p ${DESTDIR}${MAN7_DIR}
 		cp sndio.h ${DESTDIR}${INCLUDE_DIR}
-		cp -R ${SO} ${SO_LINK} ${DESTDIR}${LIB_DIR}
+		cp -R ${SO} ${SO_LINK} ${SO_LINK_MAJ} ${DESTDIR}${LIB_DIR}
 		cp sio_open.3 ${DESTDIR}${MAN3_DIR}
 		ln -sf sio_open.3 ${DESTDIR}${MAN3_DIR}/sio_close.3
 		ln -sf sio_open.3 ${DESTDIR}${MAN3_DIR}/sio_setpar.3
@@ -126,6 +127,9 @@ ${SO}:		${OBJS}
 ${SO_LINK}:
 		ln -sf ${SO} ${SO_LINK}
 
+${SO_LINK_MAJ}:
+		ln -sf ${SO} ${SO_LINK_MAJ}
+
 issetugid.o:	../bsd-compat/issetugid.c
 		${CC} ${CFLAGS} ${SO_CFLAGS} ${INCLUDE} ${DEFS} -c -o issetugid.o ../bsd-compat/issetugid.c