gdb: Convert language la_class_name_from_physname field to a method

This commit changes the language_data::la_class_name_from_physname function
pointer member variable into a member function of language_defn.

There should be no user visible changes after this commit.

gdb/ChangeLog:

	* ada-lang.c (ada_language_data) Delete
	la_class_name_from_physname initializer.
	* c-lang.c (c_language_data): Likewise.
	(cplus_language_data): Likewise.
	(cplus_language::class_name_from_physname): New member function.
	(asm_language_data): Delete la_class_name_from_physname
	initializer.
	(minimal_language_data): Likewise.
	* d-lang.c (d_language_data): Likewise.
	* dwarf2/read.c (guess_partial_die_structure_name): Update to call
	method on language_defn class.
	(guess_full_die_structure_name): Likewise.
	* f-lang.c (f_language_data): Delete la_class_name_from_physname
	initializer.
	* go-lang.c (go_language_data): Likewise.
	* language.c (language_class_name_from_physname): Delete.
	(unk_lang_class_name): Delete.
	(unknown_language_data): Delete la_class_name_from_physname
	initializer.
	(auto_language_data): Likewise.
	* language.h (language_data): Delete la_class_name_from_physname
	field.
	(language_defn::class_name_from_physname): New function.
	(language_class_name_from_physname): Delete declaration.
	* m2-lang.c (m2_language_data): Delete la_class_name_from_physname
	initializer.
	* objc-lang.c (objc_language_data): Likewise.
	* opencl-lang.c (opencl_language_data): Likewise.
	* p-lang.c (pascal_language_data): Likewise.
	* rust-lang.c (rust_language_data): Likewise.

gdb/d-lang.c

@@ -154,8 +154,6 @@ extern const struct language_data d_language_data =
   "this",
   false,			/* la_store_sym_names_in_linkage_form_p */
   d_lookup_symbol_nonlocal,
-  NULL,				/* Language specific
-				   class_name_from_physname.  */
   d_op_print_tab,		/* Expression operators for printing.  */
   1,				/* C-style arrays.  */
   0,				/* String lower bound.  */