Take Cryptographic API outside the XXX_ALT check

The cryptographic API should not be related to whether or not
there is alternative implementation. The API should be same for regular
implementation, and for alternative implementation, so it is defined
outside of the XXX_ALT precompilation check in the cryptographic API header
diff --git a/ChangeLog b/ChangeLog
index aaf34fc..4249de7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -135,6 +135,9 @@
    * Clarify the documentation of mbedtls_ssl_setup.
    * Use (void) when defining functions with no parameters. Contributed by
      Joris Aerts. #678
+   * Put the Cryptographic API outside of the XXX_ALT macro check, so
+     alternative header file will not need to redefined the same API,
+     and to force alternative implementer to use the same API.
 
 = mbed TLS 2.7.0 branch released 2018-02-03