lib/crypto: Document what crypto code is used for, and if GnuTLS supports it

Signed-off-by: Andrew Bartlett <abartlet@samba.org>

Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Tue Feb 17 11:45:15 CET 2015 on sn-devel-104

lib/crypto/REQUIREMENTS

@@ -0,0 +1,97 @@
+A list of the crypto operations that we require, and what uses them.
+
+This list is to allow research into using external crypto libraries.
+Those possibly supported in the git version of GnuTLS are indicated as '# GNUTLS'
+
+ARCFOUR (RC4)
+ - the old SamOEMHash
+ - Password encryption on SAMR for password set/get
+ - NETLOGON SamLogon session keys
+ - Schannel
+ - genrate_random_data()
+
+ # GNUTLS
+
+DES
+ - NTLM challenge-response
+ - LSA QuerySecret et al
+ - NETLOGON SamLogon session keys
+ - ServerGetTrustInfo returned passwords
+ - RID encryption of passwords
+
+3DES
+ - NETLOGON Credentials
+
+CRC32
+ - DRSUAPI replication replicated secrets
+
+AES CFB8
+ - SCHANNEL
+ - NETLOGON SamLogon session keys
+
+AES 128
+ - SMB VFS traffic analyzer
+
+AES128 CCM
+ - SMB2 2.24 SMB encryption
+ # GNUTLS
+
+AES128 GCM
+ - SMB2 3.10 SMB encryption
+ # GNUTLS
+
+AES128 CMAC
+ - SMB2 0x224 SMB Signing
+
+MD4
+ - NTLM password hash
+ - genrate_random_number()
+
+MD5
+ - NTLM2
+ - SCHANNEL
+ - NTLMSSP
+ - NETLOGON computer credentials
+ - DRSUAPI blob encryption
+ - SAMR/wkssvc password change/set encryption
+ - vfs_fruit
+ - vfs_streams_xattr
+ - passdb old password history format
+ - dsdb password_hash module
+ - SMB1 SMB signing
+ - NTP ntp_signd
+
+ # GNUTLS
+
+HMAC-MD5
+ - NTLMv2
+
+ # GNUTLS
+
+HMACSHA256
+ - SMB2 < 2.24 SMB signing
+ - SMB2 Key derivation
+
+ # GNUTLS
+
+HMACSHA1
+ - BackupKey ServerWrap
+
+ # GNUTLS
+
+SHA256
+ - Security Descriptor hash for vfs_acl_xattr
+ - oLschema2ldif
+
+ # GNUTLS
+
+SHA512
+ - SMB2 Pre-auth integrity verification
+ - BackupKey ClientWrap
+
+ # GNUTLS
+
+RSA
+ - BackupKey ClientWrap
+
+ # GNUTLS