Log message:
py-cpplint: fix sandboxed builds

In (some) sandboxed environments, this would fail to build due to a
series of failures relating to setup requirements. It prefers py-pip,
so simply explicitly make that a TOOL_DEPENDS.

Log message:
devel/py-cpplint: import py-cpplint-1.5.1

Cpplint is a command-line tool to check C/C++ files for style issues
following Google's C++ style guide. Cpplint is developed and
maintained by Google Inc.

While Google maintains cpplint, Google is not (very) responsive to
issues and pull requests, this fork aims to be (somewhat) more open
to add fixes to cpplint to enable fixes, when those fixes make
cpplint usable in wider contexts.