* Fixes a number of "<function>: not all control paths return a value" warnings on MSVC.
* Introduces the UNREACHABLE global macro and uses it instead of conditionally compiled switch defaults.
* Move cNBTParseErrorCategory from FastNBT.h into FastNBT.cpp to prevent bad calls to message()
* Replaces AppendVPrintf with fmt::sprintf
* fmt::ArgList now used as a type safe alternative to varargs.
* Removed SIZE_T_FMT compatibility macros. fmt::sprintf is fully portable and supports %zu.
* Adds FLOG functions to log with fmt's native formatting style.
* Renaming changes:
* macro prefix "POLARSSL" -> "MBEDTLS"
* functions now prefixed with "mbedtls_"
* rename PolarSSL++ -> mbedTLS++
* rename polarssl submodule
* Use mbedtls' AES-CFB8 implementation.
* Add cSslConfig to wrap mbedtls_ssl_config
* Update cTCPLink and cBlockingSslClientSocket to use cSslConfig
* Use cSslConfig in cHTTPServer
* Use cSslConfig for cMojangAPI::SecureRequest
* CI Fixes
* Set -fomit-frame-pointer on the right target
