Update certificate to fix failing test
Clean up preparation and testing of src/polarssl git submodule
o Move all submodule preparatory scripting inline so it is visible
o Support multiple versions of polarssl, by providing version specific
   patch files for their src/polarssl/include/polarssl/config.h
o Support patch for PolarSSL 1.3.4, in preparation for future support
o Improve tests/cert_tests.c to detect an invalid tests/ca/m2-cert.pem,
  and adjust its certificate validation expectations accordingly,
  while ensuring that the maintainer is warned to update the cert.
o Fix tests/runtests.sh to allow passage of stderr output to maintainer
Restore execution of submodule init, and deinit submodule in 'make pristine'
Compatibility with older (eg. mac) sed