API: Replace HTTP Basic auth with static key in custom header

Given that the key is sent in a custom header, this should prevent
any possible CSRF attacks.

Fixes #1769.
Fixes documentation for remotehttp-backend.
Still needs clarification on the SSL information.
Only add LUA_CFLAGS and LUA_LIBS if we have lua
cleanup lua backend test dir
Cleanup linking with YaHTTP

Replace the hardcoded paths with variables.
Rename polarssl-1.3.2 to polarssl

Makes upgrading in the future much easier
since we don't hardcode the version number everywhere.
Upgrade to polarssl 1.3.8

Upstream commit 1910aa78a367
Disable aesni for now
Use an automake variable for server building

Since automake knows all possible values of this variable
up front, it can determine what goes into DIST_SUBDIRS
automagically.
Remove leftover BOOST_CPPFLAGS and THREADFLAGS

They're now set in configure.ac
Memory allocating with new[] should be freed with delete[]
Merge pull request #1806 from mind04/lua-test

cleanup lua backend test dir
Merge pull request #1809 from rubenk/remove-last-remnant-of-boost-cppflags

Remove leftover BOOST_CPPFLAGS and THREADFLAGS
Merge pull request #1807 from rubenk/cleanup-linking-with-yahttp

Cleanup linking with YaHTTP
Merge pull request #1804 from rubenk/conditionalize-lua

Only add LUA_CFLAGS and LUA_LIBS if we have lua
Merge pull request #1782 from zeha/api-key

API: Replace HTTP Basic auth with static key in custom header
Merge pull request #1808 from rubenk/upgrade-polarssl

Upgrade polarssl
also dist polarssl platform.h with the recursor
Merge pull request #1812 from nlyan/minor-fixes

Memory allocating with new[] should be freed with delete[]
cleanup polar update