Merge branch 'sha1-2.1' into mbedtls-2.1
* sha1-2.1:
Cleaned up negative test predicate for test case
all.sh: test with SHA-1 enabled
SHA-1 deprecation: allow it in key exchange
Allow SHA-1 in server tests, when the signature_algorithm extension is not used
Document test data makefile
X.509 tests: obey compile-time SHA-1 support option
Allow SHA-1 in test scripts
Test that SHA-1 defaults off
Allow SHA-1 in SSL renegotiation tests
Test that X.509 verification rejects SHA-256 by default
Allow SHA-1 in X.509 and TLS tests
X.509 self-tests: replaced SHA-1 certificates by SHA-256
Added SHA256 test certificates
Remove SHA-1 in TLS by default