link readline directly to ncurses since it needs symbols from it

upstream readline does this on purpose (no direct linking), but
it doesn't make much sense in a Linux world

--- a/support/shobj-conf
+++ b/support/shobj-conf
@@ -42,7 +42,7 @@
 SHOBJ_LIBS=
 
 SHLIB_XLDFLAGS=
-SHLIB_LIBS=
+SHLIB_LIBS=-lncurses
 
 SHLIB_DOT='.'
 SHLIB_LIBPREF='lib'