Bump go version to 1.21

Allows us to use the much faster builtin min/max functions
for two variable min/max

tools/utils/images/loading.go

@@ -216,7 +216,7 @@ func check_resize(frame *ImageFrame, filename string) error {
 }
 
 func (frame *ImageFrame) set_delay(min_gap, delay int) {
-	frame.Delay_ms = int32(utils.Max(min_gap, delay) * 10)
+	frame.Delay_ms = int32(max(min_gap, delay) * 10)
 	if frame.Delay_ms == 0 {
 		frame.Delay_ms = -1 // gapless frame in the graphics protocol
 	}
@@ -308,7 +308,7 @@ func parse_identify_record(ans *IdentifyRecord, raw *IdentifyOutput) (err error)
 		if err != nil {
 			return fmt.Errorf("Invalid gap value in identify output: %s", raw.Gap)
 		}
-		ans.Gap = utils.Max(0, ans.Gap)
+		ans.Gap = max(0, ans.Gap)
 	}
 	area, pos, found := strings.Cut(raw.Canvas, "+")
 	ok := false

tools/utils/misc.go

@@ -3,6 +3,7 @@
 package utils
 
 import (
+	"cmp"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -98,19 +99,13 @@ func sort_with_key[T any, C constraints.Ordered](stable bool, s []T, key func(a
 	for i, x := range s {
 		temp[i].val, temp[i].key = x, key(x)
 	}
-	cmp := func(a, b t) int {
-		if a.key < b.key {
-			return -1
-		}
-		if a.key > b.key {
-			return 1
-		}
-		return 0
+	key_cmp := func(a, b t) int {
+		return cmp.Compare(a.key, b.key)
 	}
 	if stable {
-		slices.SortStableFunc(temp, cmp)
+		slices.SortStableFunc(temp, key_cmp)
 	} else {
-		slices.SortFunc(temp, cmp)
+		slices.SortFunc(temp, key_cmp)
 	}
 	for i, x := range temp {
 		s[i] = x.val

tools/utils/style/indent-and-wrap.go

@@ -507,7 +507,7 @@ func (self *wrapper) wrap_text(text string) []string {
 }
 
 func new_wrapper(opts WrapOptions, width int) *wrapper {
-	width = utils.Max(2, width)
+	width = max(2, width)
 	ans := wrapper{indent: opts.Indent, width: width, trim_whitespace: opts.Trim_whitespace, indent_width: wcswidth.Stringwidth(opts.Indent)}
 	if opts.Ignore_lines_containing != "" {
 		ans.ignore_lines_containing = utils.Splitlines(opts.Ignore_lines_containing)