Ports: Switch to new ports system (#594)

Much redundancy is removed from package scripts with this system.
It also supports simple dependency management, uninstalling (through
BSD ports style plist files), cleaning up after itself (with clean,
clean_dist, clean_all commands), etc.

Ports/mbedtls/patches/add-missing-includes.patch

@@ -0,0 +1,22 @@
+diff -u -r mbedtls/library/ssl_tls.c mbedtls-patched/library/ssl_tls.c
+--- mbedtls/library/ssl_tls.c	2019-06-18 23:23:28.000000000 +1000
++++ mbedtls-patched/library/ssl_tls.c	2019-08-05 00:36:37.049255960 +1000
+@@ -49,6 +49,7 @@
+ #include "mbedtls/platform_util.h"
+ 
+ #include <string.h>
++#include <stdint.h>
+ 
+ #if defined(MBEDTLS_X509_CRT_PARSE_C)
+ #include "mbedtls/oid.h"
+diff -u -r mbedtls/library/x509_crt.c mbedtls-patched/library/x509_crt.c
+--- mbedtls/library/x509_crt.c	2019-06-18 23:23:28.000000000 +1000
++++ mbedtls-patched/library/x509_crt.c	2019-08-05 00:24:22.606023827 +1000
+@@ -75,6 +75,7 @@
+ #include <sys/types.h>
+ #include <sys/stat.h>
+ #include <dirent.h>
++#include <unistd.h>
+ #endif /* !_WIN32 || EFIX64 || EFI32 */
+ #endif
+