switch from boost int types to <stdint.h>

Rebased-By: Wladimir J. van der Laan <laanwj@gmail.com>
Rebased-From: 4b61a6a, 3e74ac2, d56e30c
Github-Pull: #4129
remove ParseString(...) which is never used

Rebased-By: Wladimir J. van der Laan <laanwj@gmail.com>
Rebased-From: be54b87
gitian: Add OSX build descriptors

Github-Pull: #4185
Rebased-By: Wladimir J. van der Laan
Rebased-From: 1a97b22