rtl.h (get_pool_constant, [...]): Replace rtx parameters with const_rtx parameters.

rtl.h (get_pool_constant, [...]): Replace rtx parameters with const_rtx parameters.

gcc/
	* rtl.h (get_pool_constant, rtx_referenced_p): Replace rtx parameters
	with const_rtx parameters.
	* varasm.c (get_pool_constant): Likewise.
	* rtlanal.c (rtx_referenced_p_1): Delete.
	(rtx_referenced_p): Use FOR_EACH_SUBRTX instead of for_each_rtx.
	Assert that the rtx we're looking for is nonnull.  Allow searches
	for constant pool SYMBOL_REFs.

From-SVN: r214654