Log Message:
bochs: Various fixes and cleanups.

- Move options to options.mk.
- Make the -x11 option work by not unconditionally linking
  -lX11 in the Makefile.
- Fix the PLIST on non-NetBSD OSes.
- Add SDL support for audio output on various platforms.
- Document some patches and otherwise delint.

XXX: the "debug" option is broken. The debug interface these
days requires wxGTK, but I couldn't get that to work anyhow.

Verified to build on NetBSD and Linux (more testing and reports
welcome); via drecklypkg