re PR middle-end/52515 (build fails on cris-elf in unwind-dw2.c,  x86_64-unknown-linux-gnu in bid_binarydecimal.c)

gcc/
	PR middle-end/52515
	* rtl.h (pc_rtx, cc0_rtx, ret_rtx, simple_return_rtx): Add GTY markers.

From-SVN: r185028