Features
   * Add a function to export ECP keypair parameters.
     Fixes #4838.

Features
   * Add mbedtls_ecp_export() function to export ECP
     keypair parameters. Fixes #4838.

Add function name to changelog
Add function name to changelog

Signed-off-by: Przemek Stekiel <1d381786fa074b2f2333843496828c8e4357e75f@mobica.com>
