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/simulation/SimGyro.h

@@ -15,6 +15,8 @@
 
 using namespace gazebo;
 
+namespace frc {
+
 class SimGyro {
  public:
   explicit SimGyro(std::string topic);
@@ -32,3 +34,5 @@ class SimGyro {
   void positionCallback(const msgs::ConstFloat64Ptr& msg);
   void velocityCallback(const msgs::ConstFloat64Ptr& msg);
 };
+
+}  // namespace frc