BUG #13788: compile error in generic_msvc.h

The following bug has been logged on the website:

Bug reference:      13788
Logged by:          paul moore
Email address:      paul.moore@centrify.com
PostgreSQL version: 9.5beta1
Operating system:   win server 2012
Description:

vs 2015, compiling spi execq sample

vc complains about this

1>c:\Program
Files\PostgreSQL\9.5\include\server\port/atomics/generic-msvc.h(91): error
C2664: 'LONG64 _InterlockedCompareExchange64(volatile LONG64
*,LONG64,LONG64)': cannot convert argument 1 from 'volatile uint64 *' to
'volatile LONG64 *'

same for the add64 function a few lines later