www/node: build on i386

A recent change to V8 changed how mapped shared libraries were
discovered on FreeBSD, changing from using /proc/self/maps to using
sysctl with KERN_PROC_VMMAP. Unforcunately, this change fails to build
on i386 (and probably other 32-bit platforms) due to the use of
reinterpret_cast to change uint64_t to uintptr_t. This is an invalid
cast. The uin64_t should be static_cast to uintptr_t for it to work on
all platforms.

While here, bump the libuv dependency that I missed when upgrading to
13.6.0

PR: 243798
Reported by: Martin Birgmeier <d8zNeCFG@aon.at>
Reported by: paul beard <paulbeard@gmail.com>
Reported by: pkg-fallout@FreeBSD.org
Sponsored by: Miles AS