Add extension msgpack support (#543)

config/ext.json

@@ -360,6 +360,15 @@
             "zlib"
         ]
     },
+    "msgpack": {
+        "support": {
+            "BSD": "wip"
+        },
+        "type": "external",
+        "source": "msgpack",
+        "arg-type-unix": "with",
+        "arg-type-win": "enable"
+    },
     "mysqli": {
         "type": "builtin",
         "arg-type": "with",

config/source.json

@@ -514,6 +514,16 @@
             "path": "LICENSE"
         }
     },
+    "msgpack": {
+        "type": "url",
+        "url": "https://pecl.php.net/get/msgpack",
+        "path": "php-src/ext/msgpack",
+        "filename": "msgpack.tgz",
+        "license": {
+            "type": "file",
+            "path": "LICENSE"
+        }
+    },
     "ncurses": {
         "type": "filelist",
         "url": "https://ftp.gnu.org/pub/gnu/ncurses/",