libdl: Add powerpc large memory and small data support.

- Add support for architecure sections that can be handled by the
  architecture back end.

- Add trampoline/fixup support for PowerPC. This means the PowerPC
  now supports large memory loading of applications.

- Add a bit allocator to manage small block based regions of memory.

- Add small data (sdata/sbss) support for the PowerPC. The support
  makes the linker allocated small data region of memory a global
  resource available to libdl loaded object files.

Updates #3687
Updates #3685

cpukit/libdl/rtl-mdreloc-lm32.c

@@ -19,6 +19,38 @@ rtems_rtl_elf_section_flags (const rtems_rtl_obj* obj,
   return 0;
 }
 
+uint32_t
+rtems_rtl_elf_arch_parse_section (const rtems_rtl_obj* obj,
+                                  int                  section,
+                                  const char*          name,
+                                  const Elf_Shdr*      shdr,
+                                  const uint32_t       flags)
+{
+  (void) obj;
+  (void) section;
+  (void) name;
+  (void) shdr;
+  return flags;
+}
+
+bool
+rtems_rtl_elf_arch_section_alloc (const rtems_rtl_obj* obj,
+                                  rtems_rtl_obj_sect*  sect)
+{
+  (void) obj;
+  (void) sect;
+  return false;
+}
+
+bool
+rtems_rtl_elf_arch_section_free (const rtems_rtl_obj* obj,
+                                  rtems_rtl_obj_sect*  sect)
+{
+  (void) obj;
+  (void) sect;
+  return false;
+}
+
 bool
 rtems_rtl_elf_rel_resolve_sym (Elf_Word type)
 {