Update git submodules

* Update external/libcppbor from branch 'master'
  to 0f9cd2d79d08df69f966b8a10bd54e691a42fa6d
  - Improvements to cppbor
    
    1. Add pretty-printing (moved from IdentityCredentialSupport)
    2. Add EncodedItem to make it easy to add already-encoded CBOR.
    3. Add Map canonicalization.
    4. Add support for adding enums as integers.
    
    Test: cppbor_test_external
    Change-Id: I641c87567a11de4641b2fcadebe72dd832fceb51
    
  - Apply clang-format.
    
    Test: cppbor_test_external
    Change-Id: If907312dc498a241f077de40745c5908fad6c15a
    
1 file changed