Fix 9 bit hardware serial receive

https://forum.pjrc.com/threads/27093-Fix-for-9-bit-serial-receive-bug

teensy3/serial1.c

 			head = rx_buffer_head;
 			tail = rx_buffer_tail;
 			do {
-				n = UART0_D;
-				if (use9Bits && (UART0_C3 & 0x80)) n |= 0x100;
+				if (use9Bits && (UART0_C3 & 0x80)) {
+					n = UART0_D | 0x100;
+				} else {
+					n = UART0_D;
+				}
 				newhead = head + 1;
 				if (newhead >= RX_BUFFER_SIZE) newhead = 0;
 				if (newhead != tail) {

teensy3/serial2.c

 			head = rx_buffer_head;
 			tail = rx_buffer_tail;
 			do {
-				n = UART1_D;
-				if (use9Bits && (UART1_C3 & 0x80)) n |= 0x100;
+				if (use9Bits && (UART1_C3 & 0x80)) {
+					n = UART1_D | 0x100;
+				} else {
+					n = UART1_D;
+				}
 				newhead = head + 1;
 				if (newhead >= RX_BUFFER_SIZE) newhead = 0;
 				if (newhead != tail) {

teensy3/serial3.c

 	uint8_t c;
 
 	if (UART2_S1 & UART_S1_RDRF) {
-		n = UART2_D;
-		if (use9Bits && (UART2_C3 & 0x80)) n |= 0x100;
+		if (use9Bits && (UART2_C3 & 0x80)) {
+			n = UART2_D | 0x100;
+		} else {
+			n = UART2_D;
+		}
 		head = rx_buffer_head + 1;
 		if (head >= RX_BUFFER_SIZE) head = 0;
 		if (head != rx_buffer_tail) {