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/Utility.cpp

@@ -19,6 +19,8 @@
 #include "HAL/HAL.h"
 #include "nivision.h"
 
+using namespace frc;
+
 /**
  * Assert implementation.
  * This allows breakpoints to be set on an assert.
@@ -122,6 +124,8 @@ bool wpi_assertNotEqual_impl(int valueA, int valueB, const char* valueAString,
   return valueA != valueB;
 }
 
+namespace frc {
+
 /**
  * Return the FPGA Version number.
  *
@@ -221,3 +225,5 @@ std::string GetStackTrace(int offset) {
 
   return trace.str();
 }
+
+}  // namespace frc