I've built pl/v8 for PostgreSQL 9.5 both 32-bit and 64-bit.
I built basically using these instructions on my gist gist page.
I've listed below PL/V8 binaries I built for PostgreSQL 9.5 for windows 64-bit and 32-bit. These I tested with EDB PostgreSQL 9.5 windows installs and seem to work fine and also passed all regression tests. These were built with PLV8 v1.4.4.