tweaks: declare a function as const and let its allocated string leak

Avoiding this leak is more trouble than it's worth: invocation_error()
will be called seldomly, and when it is called, the user will probably
quickly exit from nano to fix things.

Also declare the speller functions as const again, so they don't give
the impression that their result can be freed.

Suggested-by: Brand Huntsman <alpha@qzx.com>

src/text.c

@@ -60,8 +60,9 @@ void do_mark(void)
 #endif /* !NANO_TINY */
 
 #if defined(ENABLE_COLOR) || defined(ENABLE_SPELLER)
-/* Return an error message about invoking the given name. */
-char *invocation_error(const char *name)
+/* Return an error message about invoking the given name.  The message
+ * should not be freed; this leak is not worth the trouble avoiding. */
+const char *invocation_error(const char *name)
 {
 	char *message, *invoke_error = _("Error invoking \"%s\"");
 
@@ -2356,7 +2357,7 @@ bool fix_spello(const char *word)
 /* Internal (integrated) spell checking using the spell program,
  * filtered through the sort and uniq programs.  Return NULL for normal
  * termination, and the error string otherwise. */
-char *do_int_speller(const char *tempfile_name)
+const char *do_int_speller(const char *tempfile_name)
 {
 	char *misspellings, *pointer, *oneword;
 	long pipesize;
@@ -2548,7 +2549,7 @@ char *do_int_speller(const char *tempfile_name)
 
 /* External (alternate) spell checking.  Return NULL for normal
  * termination, and the error string otherwise. */
-char *do_alt_speller(char *tempfile_name)
+const char *do_alt_speller(char *tempfile_name)
 {
 	int alt_spell_status;
 	size_t current_x_save = openfile->current_x;
@@ -2651,7 +2652,7 @@ void do_spell(void)
 	char *temp;
 	unsigned stash[sizeof(flags) / sizeof(flags[0])];
 		/* A storage place for the current flag settings. */
-	char *result_msg;
+	const char *result_msg;
 
 	if (ISSET(RESTRICTED)) {
 		show_restricted_warning();
@@ -2705,7 +2706,6 @@ void do_spell(void)
 		else
 			statusline(ALERT, _("Spell checking failed: %s: %s"), result_msg,
 												strerror(errno));
-		/* Don't try to free the result message; see bug #56188. */
 	} else
 		statusbar(_("Finished checking spelling"));
 }
@@ -2891,10 +2891,7 @@ void do_linter(void)
 	waitpid(pid_lint, &lint_status, 0);
 
 	if (!WIFEXITED(lint_status) || WEXITSTATUS(lint_status) > 2) {
-		char *result_msg= invocation_error(openfile->syntax->linter);
-
-		statusbar(result_msg);
-		free(result_msg);
+		statusbar(invocation_error(openfile->syntax->linter));
 		return;
 	}