Remove the Zc class as it is not part of the UCD; special case Cc-based whitespace instead.

src/categories.cpp

 {
 	switch (lookup_category(c))
 	{
-	case Cc: case Cf: case Ci: case Cn: case Co: case Cs: case Zc:
+	case Cc: case Cf: case Ci: case Cn: case Co: case Cs:
 		return C;
 	case Ll: case Lm: case Lo: case Lt: case Lu:
 		return L;

src/ctype.cpp

 
 int ucd::iscntrl(codepoint_t c)
 {
-	switch (lookup_category(c))
-	{
-	case Cc: case Zc:
-		return 1;
-	}
-	return 0;
+	return lookup_category(c) == Cc;
 }
 
 int ucd::isdigit(codepoint_t c)
 	switch (lookup_category(c))
 	{
 	case Cc: case Cf: case Ci: case Cn: case Co: case Cs:
-	case Zc: case Zl: case Zp: case Zs:
+	case Zl: case Zp: case Zs:
 		return 0;
 	}
 	return 1;
 {
 	switch (lookup_category(c))
 	{
-	case Zc: case Zl: case Zp: case Zs:
+	case Zl: case Zp: case Zs:
 		return 1;
+	case Cc:
+		switch (c) // Some control characters are also whitespace characters:
+		{
+		case 0x09: // U+0009 : CHARACTER TABULATION
+		case 0x0A: // U+000A : LINE FEED
+		case 0x0B: // U+000B : LINE TABULATION
+		case 0x0C: // U+000C : FORM FEED
+		case 0x0D: // U+000D : CARRIAGE RETURN
+		case 0x85: // U+0085 : NEXT LINE
+			return 1;
+		}
 	}
 	return 0;
 }

src/include/ucd/ucd.h

 		Sm, /**< @brief Math Symbol */
 		So, /**< @brief Other Symbol */
 
-		Zc, /**< @brief Whitespace character in the Cc category */
 		Zl, /**< @brief Line Separator */
 		Zp, /**< @brief Paragraph Separator */
 		Zs, /**< @brief Space Separator */

tools/categories.py

 {
 	switch (lookup_category(c))
 	{
-	case Cc: case Cf: case Ci: case Cn: case Co: case Cs: case Zc:
+	case Cc: case Cf: case Ci: case Cn: case Co: case Cs:
 		return C;
 	case Ll: case Lm: case Lo: case Lt: case Lu:
 		return L;