Fixed build errors integrating upstream qemu configure fixes

[valerino]

tested on ubuntu 18.04

[steev]

I don't think turning off Werror is the way to go.

The usb error is fixed via https://github.com/qemu/qemu/commit/121829cb2160e9cd82482c1542699fa589688106 this commit.

host-libusb is fixed with https://github.com/qemu/qemu/commit/9d8fa0df49af16a208fa961c2968fba4daffcc07 which deals with the libusb deprecation but allows people to build still with older versions of libusb.

And, the VTE issue can be done with this commit. https://github.com/qemu/qemu/commit/82a4f1a96ed6be87c0ef6d4393b22085751bd450#diff-e0320540bef9fc439412c472e5324303

The VTE changes actually change more upstream but since luaqemu still seems to be based on qemu 2.9.50 while upstream is 2.12, these 3 patches are all that are needed. Ideally, moving to 2.12 is best, and keeping up with upstream. I've looked into it briefly but a lot of hunks for the luajit patch fail and I haven't got the time to go through them just yet (not a developer of luaqemu, just interested in using it)