More precise packet length checking.

Issue discovered using valgrind and the Codenomicon TLS test suite.
Better check for null signature method.

Issue identified using valgrind and the Codenomicon TLS test suite.
initialize to null the SRP extension data on allocation.

Issue identified using valgrind and the Codenomicon TLS test suite.
doc update
small fixes identified by coverity.
doc update
When generating ECDSA keys, generate 256-bit keys by default.

Curves with less than 256 bits (i.e., SECP192R1 and SECP224R1) are
not widely supported.
doc update
bumped version.