libtool: support versioning on OS/2.

* build-aux/ltmain.in (func_mode_link) <*-os2*>: Set major and
versuffix.
* m4/libtool.m4 (_LT_SYS_DYNAMIC_LINKER) <*-os2*>: Set
version_type to windows. Add a version information to soname_spec.
* NEWS: Update.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>

NEWS

@@ -27,7 +27,8 @@ NEWS - list of user-visible changes between releases of GNU Libtool
   - Added -os2dllname option to work around 8 character base name
     limit on OS/2.  The option has no effect on other systems.
 
-  - Support for -export-symbols and -export-symbols-regex on OS/2.
+  - Support for DLL versioning, -export-symbols and -export-symbols-regex
+    on OS/2.
 
 
 * Noteworthy changes in release 2.4.3 (2014-10-27) [stable]

build-aux/ltmain.in

@@ -6262,7 +6262,7 @@ func_mode_link ()
 	    elif test -n "$soname_spec"; then
 	      # bleh windows
 	      case $host in
-	      *cygwin* | mingw* | *cegcc*)
+	      *cygwin* | mingw* | *cegcc* | *os2*)
 	        func_arith $current - $age
 		major=$func_arith_result
 		versuffix=-$major

m4/libtool.m4

@@ -2808,10 +2808,15 @@ openbsd* | bitrig*)
 
 os2*)
   libname_spec='$name'
+  version_type=windows
   shrext_cmds=.dll
+  need_version=no
   need_lib_prefix=no
   # OS/2 can only load a DLL with a base name of 8 characters or less.
-  soname_spec='`test -n "$os2dllname" && libname=$os2dllname; $ECHO $libname | cut -b -8 | tr . _`$shared_ext'
+  soname_spec='`test -n "$os2dllname" && libname="$os2dllname";
+    v=$($ECHO $release$versuffix | tr -d .-);
+    n=$($ECHO $libname | cut -b -$((8 - ${#v})) | tr . _);
+    $ECHO $n$v`$shared_ext'
   library_names_spec='${libname}_dll.$libext'
   dynamic_linker='OS/2 ld.exe'
   shlibpath_var=BEGINLIBPATH