PR c/85094
	* fold-const.c (operand_equal_p): Handle DEBUG_BEGIN_STMT.
	For STATEMENT_LIST, pass down OEP_LEXICOGRAPHIC and maybe
	OEP_NO_HASH_CHECK for recursive call, to avoid exponential
	checking.

	* c-c++-common/Wduplicated-branches-14.c: New test.

From-SVN: r258950