Cleanup unnecessary #nowarn statements, and clarify the ones that remain

Author: abelbraaksma

src/FSharp.Control.TaskSeq/TaskExtensions.fs

@@ -7,9 +7,9 @@ open System.Threading.Tasks
 open Microsoft.FSharp.Core.CompilerServices
 open Microsoft.FSharp.Core.LanguagePrimitives.IntrinsicOperators
 
-#nowarn "57"
-#nowarn "1204"
-#nowarn "3513"
+// note: these are *not* experimental features anymore, but they forgot to switch off the flag
+#nowarn "57" // Experimental library feature, requires '--languversion:preview'.
+#nowarn "1204" // This construct is for use by compiled F# code ans should not be used directly.
 
 [<AutoOpen>]
 module TaskExtensions =

src/FSharp.Control.TaskSeq/TaskExtensions.fsi

@@ -1,6 +1,6 @@
 namespace FSharp.Control
 
-#nowarn "1204"
+#nowarn "1204" // This construct is for use by compiled F# code ans should not be used directly.
 
 [<AutoOpen>]
 module TaskExtensions =

src/FSharp.Control.TaskSeq/TaskSeq.fs

@@ -4,8 +4,6 @@ open System.Collections.Generic
 open System.Threading
 open System.Threading.Tasks
 
-#nowarn "57"
-
 // Just for convenience
 module Internal = TaskSeqInternal
 

src/FSharp.Control.TaskSeq/TaskSeq.fsi

@@ -3,8 +3,6 @@ namespace FSharp.Control
 open System.Collections.Generic
 open System.Threading.Tasks
 
-#nowarn "1204"
-
 [<AutoOpen>]
 module TaskSeqExtensions =
     module TaskSeq =

src/FSharp.Control.TaskSeq/TaskSeqBuilder.fs

@@ -2,7 +2,8 @@ namespace FSharp.Control
 
 open System.Diagnostics
 
-#nowarn "57" // note: this is *not* an experimental feature, but they forgot to switch off the flag
+// note: this is *not* an experimental feature, but they forgot to switch off the flag
+#nowarn "57" // Experimental library feature, requires '--languversion:preview'.
 
 open System
 open System.Collections.Generic
@@ -12,7 +13,7 @@ open System.Runtime.CompilerServices
 open System.Threading.Tasks.Sources
 
 open FSharp.Core.CompilerServices
-open FSharp.Core.CompilerServices.StateMachineHelpers
+open FSharp.Core.CompilerServices.StateMachineHelpers // raises warning FS0057
 open FSharp.Control