Description:
------------
When you pass in a public or private keyfile path that has a tilde, there seems be 
some memory corruption that causes a segfault or weird issues the next 
time, in the same process, you attempt to authenticate with keyfiles.

If you pass full paths to the keyfiles, the problem goes away.

Test script:
---------------
// Attempt one
$connection = ssh2_connect('localhost', 22);
ssh2_auth_pubkey_file($connection, 'user', '~/.ssh/id_rsa.pub', '~/.ssh/id_rsa');

// Attempt two
$connection = ssh2_connect('localhost', 22);
ssh2_auth_pubkey_file($connection, 'user', '~/.ssh/id_rsa.pub', '~/.ssh/id_rsa');

// Attempt three
$connection = ssh2_connect('localhost', 22);
ssh2_auth_pubkey_file($connection, 'user', '~/.ssh/id_rsa.pub', '~/.ssh/id_rsa');