Tweaks to some comments

Remove some comments that are no longer needed,
and update a couple.

Author: hamishknight

Sources/_MatchingEngine/Regex/AST/Group.swift

@@ -27,7 +27,7 @@ extension AST {
       case nonCaptureReset
 
       // (?>...)
-      case atomicNonCapturing // TODO: is Oniguruma capturing?
+      case atomicNonCapturing
 
       // (?=...)
       case lookahead

Sources/_MatchingEngine/Regex/Parse/LexicalAnalysis.swift

@@ -514,7 +514,7 @@ extension Source {
   /// Try to lex a sequence of matching options.
   ///
   ///     MatchingOptionSeq -> '^' MatchingOption* | MatchingOption+
-  ///                        | MatchingOption* '-' MatchingOption+
+  ///                        | MatchingOption* '-' MatchingOption*
   ///
   mutating func lexMatchingOptionSequence(
   ) throws -> AST.MatchingOptionSequence? {
@@ -527,8 +527,8 @@ extension Source {
       adding.append(opt)
     }
 
-    // If the sequence begun with a caret '^', options can be added, so we're
-    // done.
+    // If the sequence begun with a caret '^', options can only be added, so
+    // we're done.
     if ateCaret.value {
       return .init(caretLoc: ateCaret.location, adding: adding, minusLoc: nil,
                    removing: [])

Sources/_MatchingEngine/Regex/Parse/Parse.swift

@@ -252,8 +252,6 @@ extension Parser {
   mutating func parseCCCMembers(
     into members: inout Array<CustomCC.Member>
   ) throws {
-    // FIXME: Track source locations
-
     // Parse members until we see the end of the custom char class or an
     // operator.
     while source.peek() != "]" && source.peekCCBinOp() == nil {

Sources/_MatchingEngine/Utility/MissingUnicode.swift

@@ -240,8 +240,8 @@ extension Unicode {
     case spaceSeparator = "Zs"
   }
 
-  // A list of unicode properties that can either be true or false.
-  // https://www.unicode.org/Public/UCD/latest/ucd/PropertyAliases.txt
+  /// A list of unicode properties that can either be true or false.
+  /// https://www.unicode.org/Public/UCD/latest/ucd/PropertyAliases.txt
   public enum BinaryProperty: String, Hashable {
     case asciiHexDigit = "ASCII_Hex_Digit"
     case alphabetic = "Alphabetic"
@@ -313,7 +313,9 @@ extension Unicode {
   }
 }
 
-// Oniguruma properties that are not covered by the above.
+/// Oniguruma properties that are not covered by Unicode spellings.
+/// TODO: These should become aliases for the Block (blk) Unicode character
+/// property.
 public enum OnigurumaSpecialProperty: String, Hashable {
   case inBasicLatin = "In_Basic_Latin"
   case inLatin1Supplement = "In_Latin_1_Supplement"