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/src/Encoder.cpp

@@ -12,6 +12,8 @@
 #include "LiveWindow/LiveWindow.h"
 #include "WPIErrors.h"
 
+using namespace frc;
+
 /**
  * Common initialization code for Encoders.
  *