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/Buttons/ToggleButtonScheduler.h

@@ -9,6 +9,8 @@
 
 #include "Buttons/ButtonScheduler.h"
 
+namespace frc {
+
 class Trigger;
 class Command;
 
@@ -21,3 +23,5 @@ class ToggleButtonScheduler : public ButtonScheduler {
  private:
   bool pressedLast;
 };
+
+}  // namespace frc