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/src/Utility.cpp

@@ -20,6 +20,8 @@
 #include "Timer.h"
 #include "simulation/simTime.h"
 
+using namespace frc;
+
 static bool stackTraceEnabled = false;
 static bool suspendOnAssertEnabled = false;
 
@@ -143,6 +145,8 @@ bool wpi_assertNotEqual_impl(int valueA, int valueB, const std::string& message,
   return valueA != valueB;
 }
 
+namespace frc {
+
 /**
  * Read the microsecond-resolution timer on the FPGA.
  *
@@ -205,3 +209,5 @@ static std::string demangle(char const* mangledSymbol) {
 }
 std::string GetStackTrace(int offset) { return "no stack trace on windows"; }
 #endif
+
+}  // namespace frc