Print the package name on deletion errors.

It appears this was already done in NetBSD a decade ago, hence
I just reuse the change (except our code is bad styled).

PR:		bin/160516
Approved by:	portmgr
Approved by:	re (kib)
Obtained from:	NetBSD

usr.sbin/pkg_install/delete/perform.c

@@ -324,8 +324,8 @@ pkg_do(char *pkg)
      */
     if (delete_package(FALSE, CleanDirs, &Plist) == FAIL)
 	warnx(
-	"couldn't entirely delete package (perhaps the packing list is\n"
-	"incorrectly specified?)");
+	"couldn't entirely delete package `%s'\n"
+	"(perhaps the packing list is incorrectly specified?)", pkg);
 
     if (chdir(LogDir) == FAIL) {
  	warnx("unable to change directory to %s! deinstall failed", LogDir);