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/sim/include/SensorBase.h

@@ -12,6 +12,8 @@
 #include "Base.h"
 #include "ErrorBase.h"
 
+namespace frc {
+
 /**
  * Base class for all sensors.
  * Stores most recent status information as well as containing utility functions
@@ -45,3 +47,5 @@ class SensorBase : public ErrorBase {
   static const int kRelayChannels = 8;
   static const int kPDPChannels = 16;
 };
+
+}  // namespace frc