Rework parallel port configure script option handling:

Rework parallel port configure script option handling:
- Move AC_ARG_ENABLE for secondary parallel port options:
  - These macros cause their configure options to appear unconditionally,
    so they should not be placed inside conditional logic.
  - Groups them with primary parallel port driver option.
- Update these options to show '-' instead of '_'; both still work.
- Update command help text to show host architecture/OS requirements.
- Display a warning when these options have been provided and the
  configure script will ignore the setting that the user specified.

git-svn-id: svn://svn.berlios.de/openocd/trunk@2104 b42882b7-edfa-0310-969c-e2dbd0fdcd60