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/AnalogPotentiometer.cpp

@@ -25,6 +25,11 @@ AnalogPotentiometer::AnalogPotentiometer(int channel, double fullRange,
  * @param offset The angular value (in desired units) representing the angular
  * output at 0V.
  */
+[[deprecated(
+    "Raw pointers are deprecated; if you just want to construct an "
+    "AnalogPotentiometer with its own AnalogInput, then call the "
+    "AnalogPotentiometer(int channel). If you want to keep your own copy of "
+    "the AnalogInput, use std::shared_ptr.")]]
 AnalogPotentiometer::AnalogPotentiometer(AnalogInput *input, double fullRange,
                                          double offset)
     : m_analog_input(input, NullDeleter<AnalogInput>()),