Log Message:
Update security/bearssl from 0.5 to 0.6

Changes since previous version:

+ Added general-purpose implementations of EAX and CCM modes (including
shared precomputation support for EAX).
+ Added general-purpose RSA/OAEP implementation.
+ Added general-purpose HKDF implementation.
+ Added support for CCM and CCM_8 TLS cipher suites (RFC 6655 and RFC 7251).
+ Added RSA and EC key generation.
+ Added private key encoding support ("raw" and PKCS#8 formats, both
in DER and PEM, for RSA and EC key pairs).
+ Made Base64 encoding/decoding constant-time (with regards to the
encoded data bytes).
+ Added a generic API for random seed providers.
+ Added an extra DRBG based on AES/CTR + Hirose construction for reseeding.
+ Some cosmetic fixes to avoid warnings with picky compilers.
+ Makefile fix to achieve compatibility with OpenBSD.
+ Fixed a bug in bit length computation for big integers (this was
breaking RSA signatures with some specific implementations and key lengths).
+ Made SSL/TLS client stricter in cipher suite selection (to align with
server behaviour).