Enable maintainer mode checks in all builds of non-release versions.

Use new --release-mode option to disable.
Enable all the GCC warning flags, as we now require at least GCC 4.7 anyway

Fix a few nullptr and cast warnings.
Inline kdf.cpp as all are simple forwarding calls
Fix get_cipher_mode for OCB and GCM with short tags
Add HKDF
Generalize the HKDF file reading
Generalize file reading test runner, use it for KDF and PBKDF
Direct people interested in TLS to 1.11
Fix old style cast warnings
Add a basic DTLS policy
Only service small allocations out of the mlock pool
Compile fixes for Python wrapper
merge of '022cd3c92c37dee696d0c3c0c197f8df8981ccbb'
     and '83151ac7a83013a2874f78978df5c4739b879775'
merge of '68c716734951de7d2d263d5ed5162e963d6c32be'
     and '714a603d145c840eec1464ea31d0d07c2bf640fa'
Include Perl's build flags. Bug 254
Add a simple HTTP 1.0 GET using asio (for CRLs and OCSP)
TLS in-memory session manager now requires a rng object as a
constructor argument, previously it used the global rng which caused a
serialization point across server threads.
Fix file rename in info.txt and add a check for this in configure
wget it ourselves, and include the hash of the file in the output
Give everything setting a feature test macro in build.h a version code
so application code can check for the specific API it expects without
having to keep track of what versions APIs x,y,z changed. Arbitrarily
set all current API versions to 20131128.