Log Message:
visualboyadvance-m: Various build and usability fixes.

- Disable i386 ASM, fails with PIC
- Disable OpenGL on NetBSD - segfaults on NetBSD 10.
  Needs investigation. Maybe Mesa ELF TLS again.
- Improve detection of iconv/gettext.
- Fix build of OpenAL audio plugin (OpenAL audio plugin still
  does not work, but also, this fails to build if you disable it...)

This has been sitting in my tree for a while.