Restrict the SignatureAlgorithms in SSL based on the NSS settings.

Added the NSS_USE_ALG_IN_SSL_KX flag for NSS_G/SetAlgorithmPolicy,
which specifies the allowed hash algorithms for SSL signatures.
This is only relevant in TLS 1.2 which uses the SignatureAlgorithms
extension. Older TLS versions have fixed signature algorithms and
formats.
The NSS_G/SetAlgorithmPolicy functions can be used to restrict the curves used in SSL

In particular the NSS_USE_ALG_IN_SSL_KX flag can be specified to allow a
specific curve for TLS negotiation. This will affect the advertized curves
as well.
Added functions to set and get numeric options for NSS.

Currently the only options defined allow setting the minimum
acceptable sizes for RSA, DH, and DSA keys. The SSL DH key exchange
was modified to take account for the min DH value set.
The NSS_G/SetAlgorithmPolicy functions can be used to restrict the curves used in cert verification

In particular the NSS_USE_ALG_IN_CERT_SIGNATURE flag can be specified to allow a
specific curve for certificate verification.
Check for acceptable certificate parameters when verifying signatures.

When verifying a certificate signature, check whether the curves present,
as well the sizes of the RSA and DSA public keys are accepted. This
uses the previously introduced API NSS_OptionGet().
Added config parameter.

This allows reading the "config=" value from the pkcs11.txt.
Apply the NSS policies read by the config parameter.

This commit introduces various 'dummy' OIDs to pass parameters
from the NSS to the SSL module.