Put in a check for visibility attribute support so we don't add the visibility

linker option when there is no visibility attribute support thus no visible 
external variables.  This is to get around a Sun Studio compiler version that
doesn't recognize the visibility attribute but recognizes the -xldscope option.

This commit was SVN r20902.

config/ompi_check_visibility.m4

@@ -29,7 +29,7 @@ AC_DEFUN([OMPI_CHECK_VISIBILITY],[
     AC_ARG_ENABLE(visibility, 
         AC_HELP_STRING([--enable-visibility],
             [enable visibility feature of certain compilers/linkers (default: enabled)]))
-    if test "$enable_visibility" = "no"; then
+    if test "$enable_visibility" = "no" -o "$ompi_cv___attribute__visibility" = "0"; then
         AC_MSG_CHECKING([enable symbol visibility])
         AC_MSG_RESULT([no]) 
         have_visibility=0