Specify text or binary mode in every start_writing_to_stdio_file call

changes/bug3607

@@ -0,0 +1,15 @@
+  o Minor bugfixes:
+
+    - Write several files (currently, buffer-stats, dirreq-stats, and
+      entry-stats on relays that collect those statistics, client_keys
+      and hostname files for hidden services that use authentication,
+      and (in the tor-gencert utility) newly generated identity and
+      signing keys) in text mode, on OSes that distinguish text mode
+      from binary mode (i.e. on Windows).  Previously, we wouldn't
+      specify text mode or binary mode, leading to an assertion
+      failure.  Fixes bug 3607.  Bugfix on 0.2.1.1-alpha (when the
+      DirRecordUsageByCountry option which would have triggered the
+      assertion failure was added), although this assertion failure
+      would have occurred in tor-gencert on Windows in 0.2.0.1-alpha.
+
+