* * load.c (scm_sys_search_load_path): Search for files under all

*	* load.c (scm_sys_search_load_path): Search for files under all
	extensions listed in the %load-extensions variable.  If FILENAME
	is absolute, return it unchanged, without searching the load path.
*	(scm_loc_load_extensions): New variable, pointing to
	%load-extensions' value cell.
	(scm_init_load): Initialize it, and the value it points to.
	(scm_primitive_load_path): Improve error reporting.

*	* load.c (scm_loc_load_hook): New variable, pointing to value cell
	of new Scheme variable %load-hook.
	(scm_primitive_load): Apply %load-hook to filename.