libdl: Add support for large memory programs

- Add trampolines to support relocs that are out of range on
  support architectures.

- Support not loading separate text/data sections in an object
  file if the symbol provided in the section is a duplicate.
  A base image may have pulled in part of an object and another
  part needs to be dynamically loaded.

- Refactor the unresolved handling to scale to hundreds of
  unresolved symbols when loading large number of files.

Updates #3685

cpukit/libdl/rtl.c

@@ -144,7 +144,7 @@ rtems_rtl_data_init (void)
       /*
        * Open the archives.
        */
-      rtems_rtl_archives_open (&rtl->archives, "/etc/rtl-libs.conf");
+      rtems_rtl_archives_open (&rtl->archives, "/etc/libdl.conf");
 
       /*
        * Open the unresolved table.
@@ -265,6 +265,14 @@ rtems_rtl_global_symbols (void)
   return &rtl->globals;
 }
 
+const char*
+rtems_rtl_last_error_unprotected (void)
+{
+  if (!rtl)
+    return NULL;
+  return rtl->last_error;
+}
+
 rtems_chain_control*
 rtems_rtl_objects_unprotected (void)
 {