Cleanup code about keystone

[iksteen]

I've been looking into this, there are a couple of relatively easy targets (eg. MachO and COFF writers which are irrelevant because keystone only uses a patched up version of the ELF writer which in turn makes all code dealing with the ObjectFormat part of Triple redundant).

There are also some harder targets such as debug info generation (DWARF/CodeView output and code dealing with call frame information and exception handling code) that's pretty much weaved into the rest of the code. Removing those would mean quite a few directives stop working which never made sense in the context of keystone in the first place (things like .loc).

Having all that out of the way opens paths for further code reduction such as the file handling (unless you want to maintain compatibility with the .include directive), getting rid of ELF section management (since keystone only cares about .text anyway.

I started doing some of this work in a branch: https://github.com/iksteen/keystone-beta/commits/clean-unused maybe you could have a look at it?

[aquynh]

i think your "easy targets" can be considered first. could you make a PR?