This change adds CRYPTO_memcmp, which compares two vectors of bytes in
an amount of time that's independent of their contents. It also changes
several MAC compares in the code to use this over the standard memcmp,
which may leak information about the size of a matching prefix.
(cherry picked from commit 2ee79888)

encrypted premaster secret value.
(cherry picked from commit ea34a583)

(cherry picked from commit 134c0065)

PR: 2963 and a number of others
(cherry picked from commit 4568182a)

PR: 2963 and a number of others

Submitted by: Dmitry Belyavsky, Seguei Leontiev
PR: 2821

Just a sample, real world applications would have to be cleverer.

from X509_STORE_CTX.

structures using HTTP. Add wrapper function to handle CRL download.

traditional format uses MD5 which is prohibited in FIPS mode.