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/shared/include/CircularBuffer.h

@@ -10,6 +10,8 @@
 #include <cstddef>
 #include <vector>
 
+namespace frc {
+
 /**
  * This is a simple circular buffer so we don't need to "bucket brigade" copy
  * old values.
@@ -42,4 +44,6 @@ class CircularBuffer {
   size_t ModuloDec(size_t index);
 };
 
+}  // namespace frc
+
 #include "CircularBuffer.inc"