Fixes to build on Raspberry Pi and latest jfbuild

[jdonald]

In the forum thread at https://lb.raspberrypi.org/forums/viewtopic.php?t=197981 we got JFSW running on the Raspberry Pi 3B+.

Other than automating the selection of NOASM, other fixes involve making this compatible with the latest jfbuild i.e. matching the new signature of startwin_run() and the removal of joynumhats. These should help on x86 Linux as well, including fixing #18.

[jonof]

Thanks for this PR. It arrived as I was in the middle of doing some fairly significant changes, so I'll rebase it and see what still fits. I'll also fix software-only-rendering builds. I have an ARM-based machine on order to do some experimenting with, so once it arrives I'll be ensuring the GL ES2 branch works on a non-desktop-class GPU, which should help with the Pi.

[jdonald]

Thanks for reading through the forum thread. It's great to hear there's support in the works for both GLES2 and software-only rendering.

If you've refactored everything to now compile on desktops with jfbuild's master branch, I suspect the only changes that would remain from here are using -fPIC and setting NOASM on ARM architectures.

We have a few related followup questions after getting things running on the Pi, but can relay these via email or IRC.