www/node: Update 8.6.0 -> 8.8.0

Update to the latest upstream v8.x release to address a remote DoS
vulnerability.

https://nodejs.org/en/blog/vulnerability/oct-2017-dos/
https://nodejs.org/en/blog/release/v8.8.0/

Remove post-patch rules to replace various occurrences of 'python' with
PYTHON_CMD. Upstream has done a change to ensure that the "correct"
python version is called at build time, making our post-patch steps
unnecessary.

Re-roll patches with 'make makepatch'.

Approved by: robak (mentor)
MFH: 2017Q4
Security: CVE-2017-14919
Differential Revision: https://reviews.freebsd.org/D12689