re PR ada/48835 (porting GNAT to m68k-linux)

re PR ada/48835 (porting GNAT to m68k-linux)

	PR ada/48835
	PR ada/61954
	* gcc-interface/gigi.h (enum standard_datatypes): Add ADT_realloc_decl
	(realloc_decl): New macro.
	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Variable>: Use local
	variable for the entity type and translate it as void pointer if the
	entity has convention C.
	(gnat_to_gnu_entity) <E_Function>: If this is not a definition and the
	external name matches that of malloc_decl or realloc_decl, return the
	correspoding node directly.
	(gnat_to_gnu_subprog_type): Likewise for parameter and return types.
	* gcc-interface/trans.c (gigi): Initialize void_list_node here, not...
	Initialize realloc_decl.
	* gcc-interface/utils.c (install_builtin_elementary_types): ...here.
	(build_void_list_node): Delete.
	* gcc-interface/utils2.c (known_alignment) <CALL_EXPR>: Return the
	alignment of the system allocator for malloc_decl and realloc_decl.
	Do not take alignment from void pointer types either.

From-SVN: r237850