Add two more working test cases for zip files with directories

* A test for zip file with both a redundant directory and empty
  directories that should be retained.
* A check that trrntzip -d removes the empty directories, even
  if the file has a proper TORRENTZIPPED comment.

regress/directories-2-d.test

@@ -0,0 +1,12 @@
+description strip directories from already torrentzipped archive with only empty directories
+return 0
+arguments -l -d directories-2.zip
+file directories-2.zip directories-2.tzip empty.tzip
+stdout
+Rezipping - directories-2.zip
+--------------------------------------------------
+Directory a/c/ Removed
+Directory b/ Removed
+--------------------------------------------------
+Rezipped 0 compressed files totaling 0 bytes.
+end-of-inline-data

regress/directories-2.test

@@ -0,0 +1,13 @@
+description torrentzip a zip archive with only directories, some empty
+return 0
+arguments -l directories-2.zip
+file directories-2.zip directories-2.zip directories-2.tzip
+stdout
+Rezipping - directories-2.zip
+--------------------------------------------------
+Directory a/ Removed
+Adding - a/c/ (0 bytes)...Done
+Adding - b/ (0 bytes)...Done
+--------------------------------------------------
+Rezipped 2 compressed files totaling 0 bytes.
+end-of-inline-data