Add support to select elliptic curve and signature algorithm for TLS

[ming]

This ticket will add the following enhancements to TLS:

1. selection of elliptic curve
2. selection of signature algorithm
3. reseeding of random with other entropy sources.

which may be useful to conform to ​NIAP protection profile.

[ming]

In 5472:

Fixed #1975: Add support to select elliptic curve and signature algorithm for TLS

[ming]

In 5483:

Re #1975: Add autoconf detection of OpenSSL elliptic curve and sigalg support

[riza]

In 5517:

Re #1975:

• Change autoconf detection in r5483 to compile time check.
• Don't use tls1_ec_nid2curve_id()/tls1_ec_curve_id2nid() since they are not public API.

Thanks to Alexander Traud for the suggestions.