With jumbo builds, we get spurious errors if several .cc files define
the same preprocessor macro without undefining it. This is also
disallowed by the style guide.
This patch adds a presubmit check to check that each #define is
eventually followed by a corresponding #undef. Special care has to be
taken for conditionally defined macros. Here, the logic to check that
there are not multiple defines and that they are undefined in all
cases is not perfect; it's optimistic in order to avoid false positives.

R=mstarzinger@chromium.org, machenbach@chromium.org

Bug: v8:6811
Change-Id: I55cde499399d97a5eb02fbc5ecfa34e6a8099d06
Reviewed-on: https://chromium-review.googlesource.com/657104
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47944}