syslog: remove all fprintf calls and use syslog instead

Syslog is now used for all error messages, return values in the code should be
used by programmers to see the status of the library/board and syslog can be
used to see quickly from a debugging perspective what has gone wrong. A few
cosmetics where improved as well as a mraa_set_log_level() call where the
syslog log mask can be set directly from libmraa.

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

include/mraa_internal_types.h

@@ -27,6 +27,11 @@
 
 #include "common.h"
 
+// general status failures for internal functions
+#define MRAA_PLATFORM_NO_INIT -3
+#define MRAA_IO_SETUP_FAILURE -2
+#define MRAA_NO_SUCH_IO -1
+
 /**
  * A structure representing a gpio pin.
  */