delete px4_includes.h header and update boards/ to use syslog

boards/emlid/navio2/navio_adc/navio_adc.cpp

@@ -52,6 +52,7 @@
 #include <stdio.h>
 #include <poll.h>
 #include <string.h>
+#include <stdlib.h>
 
 #define ADC_BASE_DEV_PATH "/dev/adc"
 #define ADC_SYSFS_PATH "/sys/kernel/rcio/adc/ch0"

boards/emlid/navio2/navio_rgbled/navio_rgbled.cpp

@@ -34,6 +34,8 @@
 #include <px4_posix.h>
 #include <drivers/drv_led.h>
 
+#include <string.h>
+
 #include "navio_rgbled.h"
 
 #define RGBLED_BASE_DEVICE_PATH "/dev/rgbled"

boards/emlid/navio2/navio_sysfs_rc_in/navio_sysfs_rc_in.cpp

@@ -38,6 +38,8 @@
 #include <stdio.h>
 #include <stdint.h>
 #include <unistd.h>
+#include <string.h>
+#include <stdlib.h>
 
 #include <px4_config.h>
 #include <px4_workqueue.h>