knownhost.c: Double the static buffer size when reading and writing known hosts (#409)
knownhost.c: Double the static buffer size when reading and writing known hosts (#409)

Notes:
We had a user who was being repeatedly prompted to accept a server key repeatedly. It turns out the base64-encoded key was larger than the static buffers allocated to read and write known hosts. I doubled the size of these buffers.

Credit:
Michael Buckley
libssh2/libssh2,libssh2/libssh2,libssh2/libssh2,libssh2/libssh2