crdump: fix the binary file dumping on windows
Stupid bug corrupted files with extra \r on windows.
From python manual:
On Windows, 'b' appended to the mode opens the file in binary mode, so there are also modes like 'rb', 'wb', and 'r+b'. Python on Windows makes a distinction between text and binary files; the end-of-line characters in text files are automatically altered slightly when data is read or written. This behind-the-scenes modification to file data is fine for ASCII text files, but it’ll corrupt binary data like that in JPEG or EXE files. Be very careful to use binary mode when reading and writing such files. On Unix, it doesn’t hurt to append a 'b' to the mode, so you can use it platform-independently for all binary files.
Test Plan: the crdump tests should now pass on windows as well (didn't actually run them on Windows because I don't really know how)
Reviewers: #mercurial, rmcelroy, ikostia, medson
Reviewed By: medson
Subscribers: mjpieters, medson
Differential Revision: https://phabricator.intern.facebook.com/D6151931