dhparams: Add pregenerated .c file to the repository.

dhparams: Add pregenerated .c file to the repository.

The version of dhparams.c generated by any given version of OpenSSL or
LibreSSL might work only with that version of the library.  This can be
inconvenient for cross-compiling if the "openssl" program on the build
machine has a different version from the library on the host where OVS will
run, since it could generate code that won't compile.

This commit fixes the problem by generating dhparams.c that works on the
currently important versions of OpenSSL and LibreSSL.

Submitted-at: https://github.com/openvswitch/ovs/pull/235
Signed-off-by: Eneas U de Queiroz <cote2004-github@yahoo.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>