"An improved Mach-O file type detection for sys::IdentifyFileType()

This patch add supports for single architecture mach-o files (the current implementation only support Universal Binary), and solve the signature conflict between java class and Universal Binary magics.

Note that this function will always returned dynamic library for Universal Binaries (like the current implementation) because the binary type is not include in the file header."

Patch by Jean-Daniel Dupas!

llvm-svn: 52766