key.c:1.105->1.106
make key_to_blob() return a NULL blob on failure; part of
bz#2175 from Loganaden Velvindron @ AfriNIC

init a few other things to NULL early too
move private key (de)serialization to key.c; ok djm
unbreak compilation post-krb and libwrap deprecation on OpenBSD
----------------------------
revision 1.99
date: 2013/12/06 13:34:54;  author: markus;  state: Exp;  lines: +361 -10;
new private key format, bcrypt as KDF by default; details in PROTOCOL.key;
feedback and lots help from djm; ok djm@
----------------------------