Page encryption for XtraDB

First version of page encryption for xtradb. It supports aes-encryption of pages, configurable via my.cnf and keys.txt. It extends xtradb tables with PAGE_ENCRYPTION and PAGE_ENCRYPTION_KEY table options.

i.e. CREATE TABLE test (id int, name varchar(50)) PAGE_ENCRYPTION=1 PAGE_ENCRYPTION_KEY=1;

#Configure page encryption in your central config file. (my.cnf)
innodb_data_encryption_providertype = 1 
innodb_data_encryption_providername = keys.txt
innodb_data_encryption_providerurl = /etc
innodb_data_encryption_filekey = secret

#Page encryption key file (keys.txt)
1;F5502320F8429037B8DAEF761B189D12;770A8A65DA156D24EE2A093277530142

Keyfile can be encrypted with a secret using aes-256.
i.e. openssl enc -aes-256-cbc -md sha1 -in keys.txt -out keys.enc
Page encryption will then try to decrypt your keyfile using the predefined secret.