check for libdl; refs #2

configure.in

@@ -193,10 +193,17 @@ if test "$have_stacktrace" = "yes"; then
     AC_DEFINE([NO_LTDL])
     AC_SEARCH_LIBS(compress, z,
                    [AC_MSG_RESULT([OK, found libz])],
-[AC_MSG_ERROR([zlib not found!
+[AC_MSG_ERROR([zlib (libz) not found!
 It is required for stack trace!
  - install zlib development package
  - or configure with option --enable-ltdl
+ - or configure with option --disable-stacktrace])])
+    AC_SEARCH_LIBS(dlopen, dl,
+                   [AC_MSG_RESULT([OK, found libdl])],
+[AC_MSG_ERROR([libdl not found!
+It is required for stack trace!
+ - install libdl development package
+ - or configure with option --enable-ltdl
  - or configure with option --disable-stacktrace])])
     AC_SEARCH_LIBS(bfd_openr, bfd,
                    [AC_MSG_RESULT([OK, found libbfd])],