Finish off the dummy minidriver integration:

Finish off the dummy minidriver integration:
- Try to disambiguates minidriver options from "standard" driver options.
  - Make minidummy symbols more explict about being a minidriver.
  - Move minidummy.c into minidummy directory to put it with its header.

In configure.in:
- Improve configuration option to allow new minidriver implementations:
  - Change option from --enable-minidummy to --enable-minidriver-dummy.
  - Move it to the end of the list of options.
  - Provides a clear pattern for future minidrivers.
- Update handling of HAVE_JTAG_MINIDRIVER_H:
  - Check for external jtag_minidriver.h only with --enable-ecosboard.
  - Otherwise, define it when --enable-minidriver-dummy is provided.
- Add check to ensure only one minidriver is enabled.
- When a minidriver is enabled, warn user that standard drivers are not built.
- Use proper AC_DEFINE semantics with MINIDRIVER_DUMMY.

In src/jtag/Makefile.am:
- Restructure handling of minidummy source files.
- Include minidummy driver header in the distribution.

In src/jtag/jtag.c:
- Restructure preprocessor logic to include:
  - only one minidriver, or
  - all configured standard drivers.

git-svn-id: svn://svn.berlios.de/openocd/trunk@2102 b42882b7-edfa-0310-969c-e2dbd0fdcd60