Changed const char* -> string in most of wpilibc.

The HAL will remain untouched in order to maintain C-style
compatibility. A few places in wpilibc were left as
C-style strings, especially if special formatting (eg,
elaborate uses of snprintf or sscanf) was being used.

In general, const char* was changed to std::string.
character buffers used for formatting were either
untouched, changed to std::stringstream, or changed
to std::string, depending on what was done with
the buffer.

Change-Id: I5e431ddf1cc4d9a6d534e1f21b16ea23be26e7f1

wpilibc/wpilibC++Devices/src/Gyro.cpp

@@ -88,6 +88,9 @@ Gyro::Gyro(int32_t channel) {
  * @param channel A pointer to the AnalogInput object that the gyro is connected
  * to.
  */
+[[deprecated(
+    "Raw pointers are deprecated; consider calling the Gyro constructor with "
+    "a channel number or passing a shared_ptr instead.")]]
 Gyro::Gyro(AnalogInput *channel)
     : Gyro(::std::shared_ptr<AnalogInput>(channel,
                                           NullDeleter<AnalogInput>())) {}