* expmed.c (struct init_expmed_rtl): Change all fields but
	pow2 and cint from struct rtx_def to rtx.
	(init_expmed_one_conv, init_expmed_one_mode): Adjust for that change.
	(init_expmed): Likewise.  Allocate all the 18 rtxes and ggc_free them
	at the end again.

From-SVN: r212325