makefile improvements

I was having issues getting revsh compiled on Arch Linux with OpenSSL
1.0.1i. These changes should fix compilation on Arch and also fix some
other issues with the makefile that might impact compilation elsewhere.

* Change makefile to convert PKCS#8 format key generated by newer
  versions of OpenSSL to the older RSA key format
* Decrease the number of days to 36500, because OpenSSL was silently
  failing to generate the certificate otherwise
* Add -lcrypto to gcc flags
* Use echo -e when adding newline to target_key.c