m4: Check for rl_completion_quote_character

Apparently we can't assume that people run readline recent enough
to have rl_completion_quote_character (added in readline-5.0
released in 2011). However, we can't compile without it. So if
not present, disable readline.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>

m4/virt-readline.m4

@@ -38,6 +38,19 @@ AC_DEFUN([LIBVIRT_CHECK_READLINE],[
     LIBS="$lv_saved_libs $extra_LIBS"
   fi
 
+  AC_CHECK_DECLS([rl_completion_quote_character],
+                 [], [],
+                 [[#include <stdio.h>
+                  #include <readline/readline.h>]])
+
+  if test "$ac_cv_have_decl_rl_completion_quote_character" = "no" ; then
+    if test "$with_readline" = "yes" ; then
+      AC_MSG_ERROR([readline is missing rl_completion_quote_character])
+    else
+      with_readline=no;
+    fi
+  fi
+
   # The normal library check...
   LIBVIRT_CHECK_LIB([READLINE], [readline], [readline], [readline/readline.h])