Changed Private Key Regex to be more tolerant regarding new lines at end of key file

[staecthSICKAG]

SSH.NET so far threw an unhelpful error message regarding an invalid key file if there was a new line between the key data and the end line. The changed regex now allows zero or one empty line.

This is now allowed

...
dw+2Ggyq5W5hl3PDTMTqn8Pc+cwmPdVe4bkNqxbCHe2omZXpNIgC31wrMBvkyUYv
pY8rMoBXqgm9hC5JsXzn6Z6X1kpGFhDjkNSdzx4jYzw=

-----END RSA PRIVATE KEY----- 

[Rob-Hague]

Just curious, do you know how the key was generated?

[WojciechNagorski]

LGTM

[staecthSICKAG]

Just curious, do you know how the key was generated?

Not really it was a key handed down to me from another department.
I would not discard the possibility that someone meddled with it to make it more aesthetically pleasing.