* inflow.c (generic_mourn_inferior): Call reinit_frame_cache

	* inflow.c (generic_mourn_inferior): Call reinit_frame_cache
	instead	of doing it ourself.
	* blockframe.c (reinit_frame_cache): Use code which was in
	generic_mourn_inferior so we can use this function even when
	we have switched targets.
	* corelow.c (core_detach): Call reinit_frame_cache.
	* target.c (target_detach): Don't call generic_mourn_inferior
	(revert yesterday's change, now handled by core_detach).
	* objfiles.c (free_objfile): Detach any core file if we call
	SOLIB_CLEAR.  #include target.h.