ada: Fix Ada representation of r_debug and link_map types

ada: Fix Ada representation of r_debug and link_map types

Both record types need to have their components 'aliased' to match their
C version. The mismatch could be observed when using LTO:

  warning: type of 'r_debug' does not match original declaration
       [-Wlto-type-mismatch]

  /usr/include/link.h:66:23: note: type 'struct r_debug' should match
  type 'struct  system__traceback__symbolic__module_name__build_...
   ...cache_for_all_modules__r_debug_type'

gcc/ada/

	* libgnat/s-tsmona__linux.adb (link_map, r_debug_type): Add
	'aliased' on all components.