Fix and document `%w` verb for `core:fmt`

core/fmt/doc.odin

@@ -9,6 +9,7 @@ The verbs:
 General:
 	%v     the value in a default format
 	%#v    an expanded format of %v with newlines and indentation
+	%w     an Odin-syntax representation of the value
 	%T     an Odin-syntax representation of the type of the value
 	%%     a literal percent sign; consumes no value
 	{{     a literal open brace; consumes no value

core/fmt/fmt.odin

@@ -1726,10 +1726,12 @@ fmt_bit_set :: proc(fi: ^Info, v: any, name: string = "", verb: rune = 'v') {
 
 		et := runtime.type_info_base(info.elem)
 
-		if name != "" {
-			io.write_string(fi.writer, name, &fi.n)
-		} else {
-			reflect.write_type(fi.writer, type_info, &fi.n)
+		if verb != 'w' {
+			if name != "" {
+				io.write_string(fi.writer, name, &fi.n)
+			} else {
+				reflect.write_type(fi.writer, type_info, &fi.n)
+			}
 		}
 		io.write_byte(fi.writer, '{', &fi.n)
 		defer io.write_byte(fi.writer, '}', &fi.n)
@@ -1746,9 +1748,17 @@ fmt_bit_set :: proc(fi: ^Info, v: any, name: string = "", verb: rune = 'v') {
 			}
 
 			if is_enum {
+				enum_name: string
+			 	if ti_named, is_named := info.elem.variant.(runtime.Type_Info_Named); is_named {
+					enum_name = ti_named.name
+				}
 				for ev, evi in e.values {
 					v := u64(ev)
 					if v == u64(i) {
+						if verb == 'w' {
+							io.write_string(fi.writer, enum_name, &fi.n)
+							io.write_byte(fi.writer, '.', &fi.n)
+						}
 						io.write_string(fi.writer, e.names[evi], &fi.n)
 						commas += 1
 						continue loop
@@ -2391,7 +2401,6 @@ fmt_named :: proc(fi: ^Info, v: any, verb: rune, info: runtime.Type_Info_Named)
 			     runtime.Type_Info_Dynamic_Array,
 			     runtime.Type_Info_Slice,
 			     runtime.Type_Info_Struct,
-			     runtime.Type_Info_Union,
 			     runtime.Type_Info_Enum,
 			     runtime.Type_Info_Map,
 			     runtime.Type_Info_Bit_Set,
@@ -2498,8 +2507,9 @@ fmt_matrix :: proc(fi: ^Info, v: any, verb: rune, info: runtime.Type_Info_Matrix
 		}
 	} else {
 		// Printed in Row-Major layout to match text layout
+		row_separator := ", " if verb == 'w' else "; "
 		for row in 0..<info.row_count {
-			if row > 0 { io.write_string(fi.writer, "; ", &fi.n) }
+			if row > 0 { io.write_string(fi.writer, row_separator, &fi.n) }
 			for col in 0..<info.column_count {
 				if col > 0 { io.write_string(fi.writer, ", ", &fi.n) }