revdep_check: record package information

Previously `revdep_check("foo")` didn't record the package name "foo", or the version of the foo. With this change, the following is added to the top of 00-summary.txt:

```
=========================================================================
Reverse dependency check for tourr 0.5.3
Commit 8952c3b3cf4c2d5e3d9084d248efe4ce07314cb8
=========================================================================
```