Add stock asyncplusplus port.

From vcpkg commit dbe35ceb30c688bf72e952ab23778e009a578f18.

Author: kring

native~/vcpkg/ports/asyncplusplus/portfile.cmake

@@ -0,0 +1,21 @@
+vcpkg_check_linkage(ONLY_STATIC_LIBRARY)
+
+vcpkg_from_github(
+    OUT_SOURCE_PATH SOURCE_PATH
+    REPO Amanieu/asyncplusplus
+    REF v1.2
+    SHA512 4b59ef805d4683631ef2ba51039deb210d9ba28b35021489560b0f2da6f75a68da8cb676807f9831047c997673556f69fdca0ae2081996274015e708fd6ff55e
+    HEAD_REF master
+)
+
+vcpkg_cmake_configure(
+    SOURCE_PATH "${SOURCE_PATH}"
+)
+
+vcpkg_cmake_install()
+
+vcpkg_cmake_config_fixup(CONFIG_PATH cmake PACKAGE_NAME async++)
+
+file(REMOVE_RECURSE "${CURRENT_PACKAGES_DIR}/debug/include" "${CURRENT_PACKAGES_DIR}/debug/share")
+
+file(INSTALL "${SOURCE_PATH}/LICENSE" DESTINATION "${CURRENT_PACKAGES_DIR}/share/${PORT}" RENAME copyright)

native~/vcpkg/ports/asyncplusplus/vcpkg.json

@@ -0,0 +1,17 @@
+{
+  "name": "asyncplusplus",
+  "version": "1.2",
+  "description": "Async++ is a lightweight concurrency framework for C++11",
+  "license": "MIT",
+  "supports": "!uwp",
+  "dependencies": [
+    {
+      "name": "vcpkg-cmake",
+      "host": true
+    },
+    {
+      "name": "vcpkg-cmake-config",
+      "host": true
+    }
+  ]
+}