Merge #351: CI: Fix pinning

30c5ea7 CI: Fix pinning (Tobin C. Harding)

Pull request description:

  MSRV build just broke because of a bunch of dependencies. I did not investigate why I just found a set of versions that builds.

  There are more CI fixes in the wind, this just makes the MSRV job pass because all PRs are currently held up by the failing job.

ACKs for top commit:
  apoelstra:
    ACK 30c5ea7

Tree-SHA512: 784461836c8a5824026c07ab64faa5c3db2ab414c6ab19f62e61af3b002f290c816209167646cbf7f40b6053d4a06c1ff2602e2467a4154eb485a53d6f118cdc

contrib/test.sh

@@ -16,7 +16,10 @@ fi
 # Test pinned versions.
 if cargo --version | grep ${MSRV}; then
     cargo update -p tempfile --precise 3.3.0
+    cargo update -p cc --precise 1.0.79
     cargo update -p log --precise 0.4.18
+    cargo update -p serde_json --precise 1.0.96
+    cargo update -p serde --precise 1.0.156
 fi
 
 # Integration test.