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/src/Commands/PrintCommand.cpp

@@ -10,6 +10,8 @@
 #include <cstdio>
 #include <sstream>
 
+using namespace frc;
+
 PrintCommand::PrintCommand(const std::string& message)
     : Command(((std::stringstream&)(std::stringstream("Print \"") << message
                                                                   << "\""))