New field la_varobj_ops in struct language_defn

New field la_varobj_ops in struct language_defn

This is a follow-up series to move language stuff out of varobj.c.

This patch adds a new field la_varobj_ops in struct language_defn so
that each language has varobj-related options.  Not every language
supports varobj, and the operations are identical to operations of c
languages.

'struct language_defn' is the ideal place to save all language-related
operations.  After this patch, some cleanups can be done in patch 2/2,
which removes language-related stuff completely from varobj.c.

Regression tested on x86_64-linux.

gdb:

2013-10-25  Yao Qi  <yao@codesourcery.com>

	* language.h (struct lang_varobj_ops): Declare.
	(struct language_defn) <la_varobj_ops>: New field.
	* ada-lang.c: Include "varobj.h"
	(defn ada_language_defn): Initialize field 'la_varobj_ops' by
	ada_varobj_ops.
	* c-lang.c: Include "varobj.h"
	(c_language_defn): Initialize field 'la_varobj_ops' by
	c_varobj_ops.
	(cplus_language_defn): Initialize field 'la_varobj_ops' by
	cplus_varobj_ops.
	(asm_language_defn): Initialize field 'la_varobj_ops' by
	default_varobj_ops.
	(minimal_language_defn): Likewise.
	* d-lang.c (d_language_defn): Likewise.
	* f-lang.c (f_language_defn): Likewise.
	* go-lang.c (go_language_defn): Likewise.
	* m2-lang.c (m2_language_defn): Likewise.
	* objc-lang.c (objc_language_defn): Likewise.
	* opencl-lang.c (opencl_language_defn): Likewise.
	* p-lang.c (pascal_language_defn): Likewise.
	* language.c (unknown_language_defn): Likewise.
	(auto_language_defn): Likewise.
	(local_language_defn): Likewise.
	* jv-lang.c (java_language_defn): Initialize field
	'la_varobj_ops' by java_varobj_ops.
	* varobj.c (varobj_create): Update.
	* varobj.h (default_varobj_ops): Define macro.