don't base64 encode our pushbullet API key

This causes Mysterious Failures and notification only works with it removed.
Make it build with znc 0.206

I'm not proud of the IRCNetwork.h autodetection in the Makefile.  It
probably requires GNU Make and GCC and Linux (for /dev/stdin).
Report curl error code in debug mode
Merge RsrchBoy:topic/pushbullet/no-base64-encode

See https://github.com/jreese/znc-push/pull/70

Hoping this might fix https://github.com/jreese/znc-push/issues/80