Serial: split singletons into multiple files

allows the linker to remove unneeded objects


Former-commit-id: b68a559

Author: facchinm

cores/arduino/SerialObj1.cpp

@@ -0,0 +1,5 @@
+#include "Serial.h"
+
+#if SERIAL_HOWMANY > 0
+UART _UART1_(UART1_TX_PIN, UART1_RX_PIN);
+#endif

cores/arduino/SerialObjs.cpp renamed to cores/arduino/SerialObj2.cpp

@@ -1,9 +1,5 @@
 #include "Serial.h"
 
-#if SERIAL_HOWMANY > 0
-UART _UART1_(UART1_TX_PIN, UART1_RX_PIN);
-#endif
-
 #if SERIAL_HOWMANY > 1
 UART _UART2_(UART2_TX_PIN, UART2_RX_PIN);
 #endif

cores/arduino/SerialObj3.cpp

@@ -0,0 +1,13 @@
+#include "Serial.h"
+
+#if SERIAL_HOWMANY > 2
+UART _UART3_(UART3_TX_PIN, UART3_RX_PIN);
+#endif
+
+#if SERIAL_HOWMANY > 3
+UART _UART4_(UART4_TX_PIN, UART4_RX_PIN);
+#endif
+
+#if SERIAL_HOWMANY > 4
+UART _UART5_(UART5_TX_PIN, UART5_RX_PIN);
+#endif