AP_HAL_AVR example RCInputTest created

* input works for APM2, but valid() isnt quite working yet

libraries/AP_HAL_AVR/examples/RCInputTest/Makefile

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+include ../../../AP_Common/Arduino.mk

libraries/AP_HAL_AVR/examples/RCInputTest/RCInputTest.pde

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+
+#include <AP_Common.h>
+#include <AP_HAL.h>
+#include <AP_HAL_AVR.h>
+
+const AP_HAL::HAL& hal = AP_HAL_AVR_APM2;
+
+void multiread(AP_HAL::RCInput* in) {
+    /* Multi-channel read method: */
+    uint16_t channels[8];
+    uint8_t valid;
+    valid = in->read(channels, 8);
+    hal.uart0->printf_P(PSTR("multi      read %d: %d %d %d %d %d %d %d %d\r\n"),
+            (int) valid, 
+            channels[0], channels[1], channels[2], channels[3],
+            channels[4], channels[5], channels[6], channels[7]);
+}
+
+void individualread(AP_HAL::RCInput* in) {
+    /* individual channel read method: */
+    uint8_t valid;
+    uint16_t channels[8];
+    valid = in->valid();
+    for (int i = 0; i < 8; i++) {
+        channels[i] = in->read(i);
+    }
+    hal.uart0->printf_P(PSTR("individual read %d: %d %d %d %d %d %d %d %d\r\n"),
+            (int) valid, 
+            channels[0], channels[1], channels[2], channels[3],
+            channels[4], channels[5], channels[6], channels[7]);
+}
+
+void loop (void) {
+    static int ctr = 0;
+
+    hal.gpio->write(27, 1);
+    
+    /* Cycle between using the individual read method
+     * and the multi read method*/
+    if (ctr < 500) {
+        multiread(hal.rcin);
+    } else {
+        individualread(hal.rcin);
+        if (ctr > 1000)  ctr = 0;
+    }
+    ctr++;
+
+    hal.gpio->write(27, 0);
+    hal.scheduler->delay(2);
+}
+
+void setup (void) {
+    hal.uart0->begin(115200);
+    hal.uart0->printf_P(PSTR("reading rc in:"));
+    hal.gpio->pinMode(27, GPIO_OUTPUT);
+    hal.gpio->write(27, 0);
+}
+
+
+extern "C" {
+int main (void) {
+    hal.init(NULL);
+    setup();
+    for(;;) loop();
+    return 0;
+}
+}