Update this so that I at least get a "d8" executable which can be
started :)

Local changes:
 * change MASTER_SITES to what appears to be in active use these days
 * update to version 3.28.62, the latest when I started on this update
 * Since devel/gyp has been updated so that if you include it's
   tool.mk, you get a "python" in the path, that substitution in Makefile
   has been removed
 * Instead of editing Makefile with sed, it's now patched; PYTONPATH
   is now also altered.
 * Use the pkgsrc-provided gyp and not the bundled version
 * Install a few more headers which come with the new version
 * Use "(intptr_t)pthread_self()" instead of syscall(SYS_gettid), the
   latter appears to be Linux-specific
 * Fix a type error by adding a cast to (void*)
 * Provide an ugly band-aid for a possibly missing PTHREAD_STACK_MIN
   constant (as on NetBSD)
 * Build agsinst the pkgsrc-provided icu, not the bundled third-party
   version, to avoid file name and/or version clashes
 * Do REPLACE_PYTHON on the various *.py scripts
 * Remove the workaround for thin archives, that's now done by the
   pkgsrc-provided gyp

Not sure the rpath editing is needed or correct; we'll see.