Add progspace support for Guile.

Add progspace support for Guile.

	* Makefile.in (SUBDIR_GUILE_OBS): Add scm-progspace.o.
	(SUBDIR_GUILE_SRCS): Add scm-progspace.c.
	(scm-progspace.o): New rule.
	* guile/guile-internal.h (pspace_smob): New typedef.
	(psscm_pspace_smob_pretty_printers): Declare.
	(psscm_pspace_smob_from_pspace): Declare.
	(psscm_scm_from_pspace): Declare.
	* guile/guile.c (initialize_gdb_module): Call
	gdbscm_initialize_pspaces.
	* guile/lib/gdb.scm: Export progspace symbols.
	* guile/lib/gdb/printing.scm (prepend-pretty-printer!): Add progspace
	support.
	(append-pretty-printer!): Ditto.
	* guile/scm-pretty-print.c (ppscm_find_pretty_printer_from_progspace):
	Implement.
	* guile/scm-progspace.c: New file.

	doc/
	* guile.texi (Guile API): Add entry for Progspaces In Guile.
	(GDB Scheme Data Types): Mention <gdb:progspace> object.
	(Progspaces In Guile): New node.

	testsuite/
	* gdb.guile/scm-pretty-print.exp: Add tests for objfile and progspace
	pretty-printer lookup.
	* gdb.guile/scm-pretty-print.scm (pp_s-printer): New function.
	(make-pp_s-printer): Call it.
	(make-pretty-printer-from-dict): New function.
	(lookup-pretty-printer-maker-from-dict): New function.
	(*pretty-printer*): Simplify.
	(make-objfile-pp_s-printer): New function.
	(install-objfile-pretty-printers!): New function.
	(make-progspace-pp_s-printer): New function.
	(install-progspace-pretty-printers!): New function.
	* gdb.guile/scm-progspace.c: New file.
	* gdb.guile/scm-progspace.exp: New file.