build: align minimum build dependencies with ndn-cxx

 * boost 1.65.1
 * gcc 7.4
 * clang 6.0
 * Xcode 10.0 (11.3 or later recommended)

Also improve some test cases

Change-Id: Ib81d082a19e61940fa6f1d89204ea8de8ed57940
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d9f98d8..47d9a6a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -22,8 +22,6 @@
         include:
           - compiler: g++-7
             os: ubuntu-18.04
-          - compiler: clang++-5.0
-            os: ubuntu-18.04
           - compiler: clang++-6.0
             os: ubuntu-18.04
     runs-on: ${{ matrix.os }}
@@ -37,7 +35,7 @@
           sudo apt-get -qy install ${CXX/clang++/clang}
           ${CXX} --version
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Build and test
         run: ./.jenkins
 
@@ -63,6 +61,6 @@
         with:
           xcode-version: ${{ matrix.xcode }}
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Build and test
         run: ./.jenkins