Add missing function headers

Signed-off-by: Mahyar Koshkouei <deltabeard@users.noreply.github.com>

source/error.h

@@ -5,11 +5,25 @@
 #define DECODER_INIT_FAIL	1001
 #define FILE_NOT_SUPPORTED	1002
 
+/**
+ * Struct to help error handling across threads.
+ */
 struct errInfo_t
 {
+	/* errno code or from defines listed above */
 	volatile int*	error;
-	Handle*			failEvent;
+
+	/* Extra information regarding error (Must be NULL if unused) */
 	volatile char*	errstr;
+
+	/* Event to trigger on error */
+	Handle*			failEvent;
 };
 
+/**
+ * Return string describing error number. Extends strerror to include some
+ * custom errors used in ctrmus.
+ *
+ * \param err	Error number.
+ */
 char* ctrmus_strerror(int err);