If you include #include <Arduino.h> you should have access to them.
The source code can be found in:
arduino-1.5.2\hardware\arduino\sam\system\libsam\include\tc.h
arduino-1.5.2\hardware\arduino\sam\system\libsam\source\tc.c
If you include #include <Arduino.h> you should have access to them.
The source code can be found in:
arduino-1.5.2\hardware\arduino\sam\system\libsam\include\tc.h
arduino-1.5.2\hardware\arduino\sam\system\libsam\source\tc.c