AP_HAL_Linux: add ConsoleDevice a handler for TTIN signal

In a case ArduPilot is launched as a background process without
detaching with *nohup* like this ./arduplane -C /dev/ttyAMA0 ConsoleDevice
is created and an attempt to read from it is made. This yields in a stopped
process. This is an endeavour to overcome this problem.

libraries/AP_HAL_Linux/ConsoleDevice.cpp

@@ -2,6 +2,7 @@
 #include <fcntl.h>
 #include <stdio.h>
 #include <unistd.h>
+#include <signal.h>
 
 #include <AP_HAL/AP_HAL.h>
 
@@ -31,9 +32,24 @@ bool ConsoleDevice::open()
 
     _closed = false;
 
+    if (!_set_signal_handlers()) {
+        close();
+        return false;
+    }
+
     return true;
 }
 
+bool ConsoleDevice::_set_signal_handlers(void) const
+{
+    struct sigaction sa;
+    sigemptyset(&sa.sa_mask);
+    sa.sa_handler = SIG_IGN;
+
+    return (sigaction(SIGTTIN, &sa, nullptr) == 0);
+
+}
+
 ssize_t ConsoleDevice::read(uint8_t *buf, uint16_t n)
 {
     if (_closed) {

libraries/AP_HAL_Linux/ConsoleDevice.h

@@ -19,4 +19,6 @@ private:
     int _rd_fd = -1;
     int _wr_fd = -1;
     bool _closed = true;
+
+    bool _set_signal_handlers(void) const;
 };