Update Xtensa per openocd patch. Remove autoconf generated files.

[rfoos]

The bulk of this change was to remove the autoconf generated files from git, and set executable permissions on some files for linux.

From the main openocd tree, the tools directory was added.

The xtensa target was modified per comments on the openocd tree.

A board, olimex_esp8266.cfg, was added to pull together the correct interface and target files.

It is building and running on Ubuntu 16.04.

Cheers,
Rick

Added tools from openocd.
Added bootstrap and submodules (.gitmodules)
Removed generated Makefile.in, etc.
Added README required by autoconf.
Merged xtensa changes from Thomas Schmid patch,
and applied fixes per Andreas comment.
http://openocd.zylin.com/#/c/3348/

[sysprogs]

Thanks for the pull request. Looks great except for one small thing: could you please get the autoconf-generated files back? The entire autoconf/automake system is a big mess on MinGW, so requiring the Windows users to get it makes the build a lot more complicated.

We know it's not the right way in terms of autoconf philosophy, but it saves a huge effort for Windows users to have those files checked in.

[rfoos]

I'll put them back. It was a small pain to have conflicts with different versions of autoconf and Makefile.in's.

I've switched to Msys2. It handles autoconf, and tools install/update with pacman. I think you'll find this eliminates your Makefile.in requirement.