Remove allocate_symbol et al

Remove allocate_symbol et al

This removes allocate_symbol, allocate_template_symbol, and
initialize_objfile_symbol in favor of changing the default values for
symbol members, and updating the one per-arch caller.

gdb/ChangeLog
2020-05-15  Tom Tromey  <tom@tromey.com>

	* language.c (language_alloc_type_symbol): Set
	SYMBOL_SECTION.
	* symtab.c (initialize_objfile_symbol): Remove.
	(allocate_symbol): Remove.
	(allocate_template_symbol): Remove.
	* dwarf2/read.c (fixup_go_packaging): Use "new".
	(new_symbol): Use "new".
	(read_variable): Don't call initialize_objfile_symbol.  Use
	"new".
	(read_func_scope): Use "new".
	* xcoffread.c (process_xcoff_symbol): Don't call
	initialize_objfile_symbol.
	(SYMBOL_DUP): Remove.
	* coffread.c (process_coff_symbol, coff_read_enum_type): Use
	"new".
	* symtab.h (allocate_symbol, initialize_objfile_symbol)
	(allocate_template_symbol): Don't declare.
	(struct symbol): Add copy constructor.  Change defaults.
	* jit.c (finalize_symtab): Use "new".
	* ctfread.c (ctf_add_enum_member_cb, new_symbol, ctf_add_var_cb):
	Use "new".
	* stabsread.c (patch_block_stabs, define_symbol, read_enum_type)
	(common_block_end): Use "new".
	* mdebugread.c (parse_symbol): Use "new".
	(new_symbol): Likewise.