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.
Only add LUA_CFLAGS and LUA_LIBS if we have lua
travis: enable verbose builds, fixes #1778
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
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[]