Remove SSL_OP_CISCO_ANYCONNECT.

I see no internal users and the existence of a THIRD version encoding
complicates all version-checking logic. Also convert another version check to
SSL_IS_DTLS that was missed earlier.

Change-Id: I60d215f57d44880f6e6877889307dc39dbf838f7
Reviewed-on: https://boringssl-review.googlesource.com/1550
Reviewed-by: Adam Langley <agl@google.com>
11 files changed