adding coverage extension for simpletest

3rdparty/simpletest/extensions/coverage/autocoverage.php

...simpletest/extensions/coverage/bin/php-coverage-close.php

.../simpletest/extensions/coverage/bin/php-coverage-open.php

...impletest/extensions/coverage/bin/php-coverage-report.php

3rdparty/simpletest/extensions/coverage/coverage.php

...ty/simpletest/extensions/coverage/coverage_calculator.php

.../simpletest/extensions/coverage/coverage_data_handler.php

...arty/simpletest/extensions/coverage/coverage_reporter.php

3rdparty/simpletest/extensions/coverage/coverage_utils.php

3rdparty/simpletest/extensions/coverage/coverage_writer.php

...simpletest/extensions/coverage/simple_coverage_writer.php

3rdparty/simpletest/extensions/coverage/templates/file.php

3rdparty/simpletest/extensions/coverage/templates/index.php

...est/extensions/coverage/test/coverage_calculator_test.php

...t/extensions/coverage/test/coverage_data_handler_test.php

...etest/extensions/coverage/test/coverage_reporter_test.php

...rty/simpletest/extensions/coverage/test/coverage_test.php

...mpletest/extensions/coverage/test/coverage_utils_test.php

3rdparty/simpletest/extensions/coverage/test/sample/code.php

.../extensions/coverage/test/simple_coverage_writer_test.php