Namespace all wpilibc functions/classes into "frc" namespace. (#311)

Base.h provides a backwards compatibility shim (enabled unless
NAMESPACED_WPILIB is defined) that does a "using namespace frc".
However, as some header files do not include Base.h, this may
be a breaking change in some corner cases (with an easy fix).

Fixes #218.

wpilibc/athena/include/Vision/FrcError.h

@@ -27,6 +27,10 @@
 #define ERR_CAMERA_TASK_INPUT_OUT_OF_RANGE 166210  // AxisCamera.cpp
 #define ERR_CAMERA_COMMAND_FAILURE 166211          // AxisCamera.cpp
 
+namespace frc {
+
 /* error handling functions */
 int GetLastVisionError();
 const char* GetVisionErrorText(int errorCode);
+
+}  // namespace frc