Improves regex in GTEST_ADD_TESTS to consider TEST_P.

Currently the GTEST_ADD_TESTS function will miss parameterized tests because it only considers TEST and TEST_F. This patch adds TEST_P to the list of considered tests and will run all instantiations of this parameterized test together.

This is perhaps not as correct as searching for all instantiations of this parameterized test and separating those into separate runs, but this will at least run tests that were previously missing.

For reference: https://code.google.com/p/googletest/wiki/Documentation