8.19

Changes in addition to prerelease:

Neoscrypt: Titan Xp fix
bugfix: send a second share when we find it
enable stale share detection
send stale shares when the pool supports it
API is now disabled by default
Windows: fix --background option
stratum: show reason of auth failure (when supported by the pool)

Linux users: please use this when you want to compile with CUDA 8:
https://github.com/KlausT/ccminer/archive/windows.zip

Known problems:
crash on some systems when the connection gets interrupted
verification errors under Linux with some algos (please use --no-cpu-verify option)