fix invalid conversion
fix invalid conversion

Summary:
e.g. invalid conversion from 'void\*' to 'char\*' [-fpermissive]
Closes https://github.com/facebook/watchman/pull/365

Reviewed By: sid0

Differential Revision: D3891558

Pulled By: wez

fbshipit-source-id: 8b941b38addd729489f07ea1a51f7684ca5f9111

nodakai/watchman,facebook/watchman,kwlzn/watchman,wez/watchman,kwlzn/watchman,facebook/watchman,wez/watchman,facebook/watchman,nodakai/watchman,wez/watchman,wez/watchman,facebook/watchman,nodakai/watchman,facebook/watchman,kwlzn/watchman,nodakai/watchman,wez/watchman,wez/watchman,nodakai/watchman,kwlzn/watchman,facebook/watchman,facebook/watchman,kwlzn/watchman,nodakai/watchman,facebook/watchman,wez/watchman,kwlzn/watchman,wez/watchman,wez/watchman,facebook/watchman,nodakai/watchman,kwlzn/watchman,nodakai/watchman,nodakai/watchman