- Add gcov flushes that will happen within the test bundles to also capture
  the coverage data there. Needed if you link some of your code directly into
  the test bundles or if you have code in headers (inlines, c++ templates, etc.)
- Add a preprocessor gate to only bring in the coverage support when enabled,
  lets you add the source, and then use a Xcode Configuration to control when
  it is needed, otherwise you can end up linking coverage into your Release
  builds.

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Enable code coverage for GTM test suite in iOS 7.
Call gcov_flush at end of tests manually if GTMCodeCoverageApp is available to receive request.

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