Fix error checks after calling SetFilePointer. Refs #3953

Thanks to Eg. Especially for writing a test.

[SVN r60281]

libs/iostreams

@@ -1 +1 @@
-Subproject commit b429d69932daa10ac0c58cb1316d4cf0ee590c2b
+Subproject commit 67e832cb3b8f69becd6974c03d19c7c21d24f0a3