Client enhancements to get crtime, file magic, and PE headers data

I used MSYS2 with MINGW to build libgnurx-0.dll and magic1.dll for Windows to be able to properly use python-magic.  The installer would also need to be modified to include the file magic database magic.mgc in the client installed directory.

I removed some packing detection and checksum comparison due to it having a pretty significant performance hit on larger binaries.  It may be worth it to enable those via options when a flow is run.

This also carves off the PKCS7 certs on PE files and returns them.  There might be better ways to do this.
I believe pefile is limited to similar behavior.  What is the proper way to read the file inside of GRR without using the path?