Use MbedTLS instead of  OpenSSL
=====

1, [build mbedtls](https://github.com/ARMmbed/mbedtls)

 1.1 git clone https://github.com/ARMmbed/mbedtls.git -b mbedtls-2.24.0
 1.2 Use Arm Mbed TLS in threaded environments, enable `MBEDTLS_THREADING_C` and `MBEDTLS_THREADING_PTHREAD` in config.h, [more](https://tls.mbed.org/kb/development/thread-safety-and-multi-threading)
 1.3 make SHARED=1 && make install

2 build civetweb

 2.1 make build COPT="-DNO_SSL -DUSE_MBEDTLS" LOPT="-lmbedcrypto -lmbedtls -lmbedx509"