cmake: show crypto backend in feature summary

This was visible as an enabled package before this patch, but it missed
to show WinCNG.

Closes #1211

src/CMakeLists.txt

@@ -42,6 +42,7 @@ set(LIBSSH2_LIBVERSION 1.0.1)
 if(CRYPTO_BACKEND)
   list(APPEND PRIVATE_COMPILE_DEFINITIONS ${CRYPTO_BACKEND_DEFINE})
   list(APPEND PRIVATE_INCLUDE_DIRECTORIES ${CRYPTO_BACKEND_INCLUDE_DIR})
+  add_feature_info("Crypto backend" ON "${CRYPTO_BACKEND}")
 else()
   message(FATAL_ERROR "No suitable cryptography backend found.")
 endif()