Fix author and date annotation of renamed entries in the tree view

This fixes log parsing of renamed tree entries to always locate the last
Tab characters in the raw diff line so that the new name is found. For
renamed diff lines both the old and new file names are listed. For
example:

	:100644 100644 6968b89... 6c2f5d8... R091       doc/tigmanual.7.asciidoc        doc/tigmanual.7.adoc