Provide some more detailed instruction how to use the decompiler

[rfalke]

The readme didn't mention which of the three executables (decompile16, decompile32, decompile64) one should use.

The decompilerXX binaries don't have a help text what parameters they expect.

[uglyoldbob]

Those are a good idea to add.

[uglyoldbob]

I added a bit of code that should make it clear how the decompile executables are used. Specify -h or --help as an argument to show the usage.