Add support for Mach-0 macOS/iOS executables

[pombredanne]

See https://en.wikipedia.org/wiki/Mach-O

They have these characteristics:

• mimetype: application/x-mach-binary; charset=binary
• file type: Mach-O 64-bit x86_64 executable (with variations on arch)

we should have a basic detection to qualify these as binaries and executables.

[pombredanne]

A simple way to go may be:

def is_macho(self):
    return (
        self.filetype_file.lower().startswith('mach-o')
        or self.mimetype_file.lower().startswith("application/x-mach-binary")
    )

or from a file location

def is_macho(location):
    t = get_type(location)
    return (
        t.filetype_file.lower().startswith('mach-o')
        or t.mimetype_file.lower().startswith("application/x-mach-binary")
    )

[pombredanne]

A small truncated file is enough for testing:
For instance:
head -c 100 GoReSym_mac > bar and bar is only 100 bytes.