gdb delay guile initialization until gdbscm_finish_initialization

Like with the previous commit, this commit delays the initialisation
of the guile extension language until gdbscm_finish_initialization.

This is mostly about splitting the existing gdbscm_initialize_*
functions in two, all the calls to register_objfile_data_with_cleanup,
gdbarch_data_register_post_init, etc are moved into new _initialize_*
functions, but everything else is left in the gdbscm_initialize_*
functions.

Then the call to code previously in _initialize_guile is moved into
gdbscm_finish_initialization.

There should be no user visible changes after this commit.

gdb/ChangeLog:

	* guile/guile.c (gdbscm_set_backtrace): Add declaration.
	(gdbscm_finish_initialization): Add code moved from
	_initialize_guile.
	(_initialize_guile): Move code to gdbscm_finish_initialization.
	* guile/scm-arch.c (gdbscm_initialize_arches): Move some code into
	_initialize_scm_arch.
	(_initialize_scm_arch): New function.
	* guile/scm-block.c (gdbscm_initialize_blocks): Move some code
	into _initialize_scm_block.
	(_initialize_scm_block): New function.
	* guile/scm-frame.c (gdbscm_initialize_frames): Move some code
	into _initialize_scm_frame.
	(_initialize_scm_frame): New function.
	* guile/scm-objfile.c (gdbscm_initialize_objfiles): Move some code
	into _initialize_scm_objfile.
	(_initialize_scm_objfile): New function.
	* guile/scm-progspace.c (gdbscm_initialize_pspaces): Move some
	code into _initialize_scm_progspace.
	(_initialize_scm_progspace): New function.
	* guile/scm-symbol.c (gdbscm_initialize_symbols): Move some code
	into _initialize_scm_symbol.
	(_initialize_scm_symbol): New function.
	* guile/scm-symtab.c (gdbscm_initialize_symtabs): Move some code
	into _initialize_scm_symtab.
	(_initialize_scm_symtab): New function.
	* guile/scm-type.c (gdbscm_initialize_types): Move some code into
	_initialize_scm_type.
	(_initialize_scm_type): New function.