[wpilibc] MotorSafety::GetDescription(): Return std::string (#3390)

This is only called in an error condition, so it's not necessary to over
optimize it.

wpilibc/src/main/native/include/frc/MotorSafety.h

@@ -4,14 +4,12 @@
 
 #pragma once
 
+#include <string>
+
 #include <wpi/mutex.h>
 
 #include "frc/Timer.h"
 
-namespace wpi {
-class raw_ostream;
-}  // namespace wpi
-
 namespace frc {
 
 /**
@@ -92,7 +90,7 @@ class MotorSafety {
   static void CheckMotors();
 
   virtual void StopMotor() = 0;
-  virtual void GetDescription(wpi::raw_ostream& desc) const = 0;
+  virtual std::string GetDescription() const = 0;
 
  private:
   static constexpr double kDefaultSafetyExpiration = 0.1;