gdb: Introduce new language field la_struct_too_deep_ellipsis

gdb: Introduce new language field la_struct_too_deep_ellipsis

This commit is preparation work for a later commit, and by itself
makes no user visible change to GDB.  I've split this work into a
separate commit in order to make code review easier.

This commit adds a new field 'la_struct_too_deep_ellipsis' to the
language struct, this string will be used in the next commit to print
a language specific string from within the generic value printing
code.

In this commit I add the new field and initialise it for each
language, however at this stage the new field is never used.

gdb/ChangeLog:

	* language.h (struct language_defn) <la_struct_too_deep_ellipsis>:
	New field.
	* ada-lang.c (ada_language_defn): Initialise new field.
	* c-lang.c (c_language_defn): Likewise.
	(cplus_language_defn): Likewise.
	(asm_language_defn): Likewise.
	(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.
	* language.c (unknown_language_defn): Likewise.
	(auto_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.
	* rust-lang.c (rust_language_defn): Likewise.