SimpleLog: really simple logging

This module exists as part of the yotta tutorial.

// Log levels: note that we prefix everything with the module name. It's OK to
// use various Casing and underscore separated conventions to denote different
// types of symbols, since module names are forced to be lower case, and cannot
// include underscores (only - characters).
enum SimpleLogLevel{
    Simple_Log_Critical = 0,
    Simple_Log_Notice   = 1,
    Simple_Log_Error    = 2,
    Simple_Log_Warning  = 3,
    Simple_Log_Info     = 4,
    Simple_Log_Debug    = 100
};

// log the message at the given level
void simpleLog(enum SimpleLogLevel level, const char* msg);

// shortcut functions, still prefixed
void simpleLogError(const char* msg);
void simpleLogWarning(const char* msg);
void simpleLogInfo(const char* msg);
void simpleLogDebug(const char* msg);