* lang.opt (-fgo-relative-import-path): New option.
	* go-lang.c (go_relative_import_path): New static variable.
	(go_langhook_init): Pass go_relative_import_path to
	go_create_gogo.
	(go_langhook_handle_option): Handle -fgo-relative-import-path.
	* go-c.h (go_create_gogo): Update declaration.
	* gccgo.texi (Invoking gccgo): Document
	-fgo-relative-import-path.

From-SVN: r193008