lower_dw: cleanup, use C99

ir/be/ia32/ia32_intrinsics.c

@@ -301,10 +301,10 @@ void ia32_lower64(void)
 {
 	/* perform doubleword lowering */
 	lwrdw_param_t lower_dw_params = {
-		1,  /* little endian */
-		64, /* doubleword size */
 		ia32_create_intrinsic_fkt,
-		NULL
+		NULL,
+		64,    /* doubleword size */
+		be_is_big_endian(),
 	};
 
 	ir_prepare_dw_lowering(&lower_dw_params);

ir/be/sparc/sparc_lower64.c

@@ -125,10 +125,10 @@ static ir_entity *create_64_intrinsic_fkt(ir_type *method, const ir_op *op,
 void sparc_lower_64bit(void)
 {
 	lwrdw_param_t lower_dw_params = {
-		0,  /* big endian */
-		64, /* doubleword size */
 		create_64_intrinsic_fkt,
-		NULL
+		NULL,
+		64,    /* doubleword size */
+		be_is_big_endian(),
 	};
 
 	/* make sure opcodes are initialized */

ir/lower/lower_dw.h

@@ -40,10 +40,11 @@ typedef ir_entity *(create_intrinsic_fkt)(ir_type *method, const ir_op *op,
  * The lowering parameter description.
  */
 typedef struct lwrdw_param_t {
-	unsigned              little_endian : 1; /**< if true should be lowered for little endian, else big endian */
-	unsigned              doubleword_size;   /**< bitsize of the doubleword mode */
-	create_intrinsic_fkt *create_intrinsic;  /**< callback that creates the intrinsic entity */
-	void                 *ctx;               /**< context parameter for the creator function */
+	create_intrinsic_fkt *create_intrinsic; /**< callback that creates the intrinsic entity */
+	void                 *ctx;              /**< context parameter for the creator function */
+	unsigned short        doubleword_size;  /**< bitsize of the doubleword mode */
+	bool                  big_endian:1;     /**< target is big endian if true,
+											     else little endian */
 } lwrdw_param_t;
 
 /**