gdb: Convert la_name and la_natural_name to methods

gdb: Convert la_name and la_natural_name to methods

Convert the two language_data member variables la_name and
la_natural_name to virtual methods in language_defn struct called name
and natural_name respectively.

The virtual methods in the language_defn base class are pure virtual,
as every language must implement these, and as every language has a
unique name there's no sensible default here.

Given that every language must implement these methods I did wonder
about making this data passed into the base class constructor, but in
the end I went with the virtual method approach.  I'm open to changing
this approach if people prefer the constructor approach.

During updating the calls to language_defn::name I found in
add_set_language_command a place where we took la_name and then
capitalised the first letter to create a language name that could be
used in the documentation string.  I replaced this with a use of
natural_name instead as this seemed a better choice, in most cases
this will make no difference, as for most languages the natural_name
is just the name with the first character in upper case, but for some
languages, for example 'Open-CL' and 'Objective-C' this is not the
case.

In the case of asm_language the name is 'asm', while the natural_name
was previously 'assembly'.  I changed the natural name to 'Assembly',
this makes the documentation string case above cleaner, however, this
will change the MI output for -var-info-expression, where the 'lang'
field will change from 'assembly' to 'Assembly'.  It is possible this
could be a breaking change if a front-end is relying on the existing
name.

gdb/ChangeLog:

	* ada-lang.c (ada_language_data): Remove la_name and
	la_natural_name initializers.
	(ada_language::name): New member function.
	(ada_language::natural_name): New member function.
	* c-lang.c (c_language_data): Remove la_name and
	la_natural_name initializers.
	(c_language::name): New member function.
	(c_language::natural_name): New member function.
	(cplus_language_data): Remove la_name and
	la_natural_name initializers.
	(cplus_language::name): New member function.
	(cplus_language::natural_name): New member function.
	(asm_language_data): Remove la_name and
	la_natural_name initializers.
	(asm_language::name): New member function.
	(asm_language::natural_name): New member function.
	(minimal_language_data): Remove la_name and
	la_natural_name initializers.
	(minimal_language::name): New member function.
	(minimal_language::natural_name): New member function.
	* compile/compile.c (compile_to_object): Update call to
	lanugage_defn::name.
	* d-lang.c (d_language_data): Remove la_name and
	la_natural_name initializers.
	(d_language::name): New member function.
	(d_language::natural_name): New member function.
	* expprint.c (print_subexp_standard): Update call to
	language_defn::name.
	(dump_raw_expression): Likewise
	(dump_prefix_expression): Likewise.
	* f-lang.c (f_language_data): Remove la_name and
	la_natural_name initializers.
	(f_language::name): New member function.
	(f_language::natural_name): New member function.
	* go-lang.c (go_language_data): Remove la_name and
	la_natural_name initializers.
	(go_language::name): New member function.
	(go_language::natural_name): New member function.
	* language.c (show_language_command): Update call to
	language_defn::name.
	(set_language_command): Likewise.
	(language_enum): Likewise.
	(language_str): Likewise.
	(add_set_language_command): Likewise, use
	language_defn::natural_name in the doc string.
	(unknown_language_data): Remove la_name and
	la_natural_name initializers.
	(unknown_language::name): New member function.
	(unknown_language::natural_name): New member function.
	(auto_language_data): Remove la_name and
	la_natural_name initializers.
	(auto_language::name): New member function.
	(auto_language::natural_name): New member function.
	(language_lookup_primitive_type_as_symbol): Update call to
	language_defn::name.
	* language.h (language_data): Remove la_name and la_natural_name
	member variables.
	(language_defn::name): New member function.
	(language_defn::natural_name): New member function.
	* m2-lang.c (m2_language_data): Remove la_name and
	la_natural_name initializers.
	(m2_language::name): New member function.
	(m2_language::natural_name): New member function.
	* mi/mi-cmd-var.c (mi_cmd_var_info_expression): Update call to
	language_defn::natural_name.
	* objc-lang.c (objc_language_data): Remove la_name and
	la_natural_name initializers.
	(objc_language::name): New member function.
	(objc_language::natural_name): New member function.
	* opencl-lang.c (opencl_language_data): Remove la_name and
	la_natural_name initializers.
	(opencl_language::name): New member function.
	(opencl_language::natural_name): New member function.
	* p-lang.c (pascal_language_data): Remove la_name and
	la_natural_name initializers.
	(pascal_language::name): New member function.
	(pascal_language::natural_name): New member function.
	* rust-lang.c (rust_language_data): Remove la_name and
	la_natural_name initializers.
	(rust_language::name): New member function.
	(rust_language::natural_name): New member function.
	* symtab.c (lookup_language_this): Update call to
	language_defn::name.