[3025] Update the error message for old boost

Tell more details about what the problem is.

configure.ac

@@ -914,7 +914,9 @@ AC_SUBST(BOOST_MAPPED_FILE_CXXFLAG)
 
 if test "$BOOST_OFFSET_PTR_OLD" = "yes" -a "$use_shared_memory" = "yes" ; then
     AC_MSG_ERROR([You're trying to compile against boost older than 1.48 with
-shared memory. This is known to cause problems under certain situations.
+shared memory. Older versions of boost have a bug which causes segfaults in
+offset_ptr implementation when compiled by GCC with optimisations enabled.
+See ticket #3025 for details.
 
 Either update boost to newer version or use --without-shared-memory.
 Note that most users likely don't need shared memory support.