Use XOBNEW/XOBNEWVEC/OBSTACK_ZALLOC when possible

Use XOBNEW/XOBNEWVEC/OBSTACK_ZALLOC when possible

Since XOBNEW/XOBNEWVEC/OBSTACK_ZALLOC are now poisoned to prevent using
them with non-trivially-constructible objects, it is worth using them
over plain obstack_alloc.  This patch changes the locations I could find
where we can do that change easily.

gdb/ChangeLog:

	* ada-lang.c (cache_symbol): Use XOBNEW and/or XOBNEWVEC and/or
	OBSTACK_ZALLOC.
	* dwarf2-frame.c (dwarf2_build_frame_info): Likewise.
	* hppa-tdep.c (hppa_init_objfile_priv_data): Likewise.
	* mdebugread.c (mdebug_build_psymtabs): Likewise.
	(add_pending): Likewise.
	(parse_symbol): Likewise.
	(parse_partial_symbols): Likewise.
	(psymtab_to_symtab_1): Likewise.
	(new_psymtab): Likewise.
	(elfmdebug_build_psymtabs): Likewise.
	* minsyms.c (terminate_minimal_symbol_table): Likewise.
	* objfiles.c (get_objfile_bfd_data): Likewise.
	(objfile_register_static_link): Likewise.
	* psymtab.c (allocate_psymtab): Likewise.
	* stabsread.c (read_member_functions): Likewise.
	* xcoffread.c (xcoff_end_psymtab): Likewise.