tryopen already tests get_num_entries; convert new test to that and
remove duplicates.

--HG--
branch : HEAD

regress/open_empty_2.test

diff --git a/regress/open_empty_2.test b/regress/open_empty_2.test
new file mode 100644
index 0000000..0f6e215
--- /dev/null
+++ b/regress/open_empty_2.test
@@ -0,0 +1,6 @@
+# zip_open: 0 size file is recognized as empty zip
+program tryopen
+file testfile.txt testfile.txt testfile.txt
+args testfile.txt
+return 0
+stdout opening `testfile.txt' succeeded, 0 entries