Intercept SIGINT signal on tests suites

If the function `pcntl_signal()` exists creates an signal handler for SIGINT which prints the summary of test suite and generates code coverage reports.
Move on `PHPUnit_TextUI_TestRunner` all code which prints results and generates coverage from `doRun()` method to `doReports()` method.

**See it working**: https://asciinema.org/a/14111
I put this in the test name to represents the interruption in a terminal (Ctlr+C) since most tests I saw had just command line as test description.