Ports: Remove some config.sub patches and download a fresh one if needed

All of these patches did the same thing, which is already in upstream
config.sub.
With this change, we need only add `use_fresh_config_sub=true` to
the package.sh file.
Note that this is not done automatically in case the port has a modified
config.sub file.

Ports/libpng/package.sh

@@ -2,6 +2,7 @@
 port=libpng
 version=1.6.37
 useconfigure=true
+use_fresh_config_sub=true
 files="https://download.sourceforge.net/libpng/libpng-${version}.tar.gz libpng-${version}.tar.gz daeb2620d829575513e35fecc83f0d3791a620b9b93d800b763542ece9390fb4"
 auth_type=sha256
 depends=("zlib")

Ports/libpng/patches/detect.patch

@@ -1,11 +0,0 @@
---- config.sub	2021-03-03 22:42:25.065684142 +0100
-+++ libpng-1.6.37/config.sub	2021-03-03 22:43:50.611720741 +0100
-@@ -1390,7 +1390,7 @@
- 	      | -powermax* | -dnix* | -nx6 | -nx7 | -sei* | -dragonfly* \
- 	      | -skyos* | -haiku* | -rdos* | -toppers* | -drops* | -es* \
- 	      | -onefs* | -tirtos* | -phoenix* | -fuchsia* | -redox* | -bme* \
--	      | -midnightbsd*)
-+	      | -midnightbsd* | -serenity*)
- 	# Remember, each alternative MUST END IN *, to match a version number.
- 		;;
- 	-qnx*)