Function resurrect_labels

* Resurrect the labels stored in the CTF data, returning the index associated * with a label provided by the caller. There are several cases, outlined * below. Note that, given two labels, the one associated with the lesser type * index is considered to be older than the other. * * 1. matchlbl == NULL - return the index of the most recent label. * 2. matchlbl == "BASE" - return the index