Add msan CI run

Now that all memory errors are fixed.

Ref #220

.github/workflows/ci.yml

     - name: make check
       run: LSAN_OPTIONS=fast_unwind_on_malloc=0 make check
 
+  msan:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: dependencies
+      run: sudo apt-get update && sudo apt-get install libpcaudio-dev libsonic-dev ronn kramdown clang
+    - name: autoconf
+      run: ./autogen.sh ; chmod -x INSTALL m4/*.m4
+    - name: configure
+      run: CXX=clang++ CC=clang CXXFLAGS="-fsanitize=memory -fsanitize-memory-track-origins=2 -g -Og" CFLAGS="-fsanitize=memory -fsanitize-memory-track-origins=2 -g -Og" ./configure --without-pcaudiolib
+    - name: make
+      run: make
+    - name: make check
+      run: make check
+
   tsan:
 
     runs-on: ubuntu-latest