clock: Add dummy data to stub so that it compiles

As part of the work in #421.

Author: petertseng

exercises/clock/HINTS.md

@@ -12,5 +12,6 @@ The function `fromInteger`, from `Num`, must convert minutes
 to 24 hour clock time. It is not necessary to have a sensible
 implementation of `abs` or `signum`.
 
-Your can use the provided signatures if you are unsure about the types, but
-don't let them restrict your creativity.
+You will find a dummy data declaration and type signatures already in place,
+but it is up to you to define the functions and create a meaningful data type,
+newtype or type synonym.

exercises/clock/src/Clock.hs

@@ -1,5 +1,7 @@
 module Clock (clockHour, clockMin, fromHourMin, toString) where
 
+data Clock = Dummy
+
 clockHour :: Clock -> Int
 clockHour = undefined