Fixing #380 where const aggregates were copied by value.

resources/lib/std/io.c3

@@ -60,7 +60,7 @@ enum Seek
     END = 2
 }
 
-errtype IoError
+optenum IoError
 {
     FILE_NOT_FOUND,
     FILE_NOT_SEEKABLE,

resources/lib/std/mem.c3

@@ -25,7 +25,7 @@ enum AllocationKind
     FREE,
 }
 
-errtype AllocationFailure
+optenum AllocationFailure
 {
     OUT_OF_MEMORY
 }