Split main jtag.c file into two layers:

Split main jtag.c file into two layers:
- src/jtag/core.c: contains the low-level JTAG TAP and scanning routines.
- src/jtag/tcl.c: contains high-level JTAG TCL commands that use the core.
- Remove static keywords from routines in core.c, extern from tcl.c:
  - jtag, jtag_interface global variables
  - jtag_{examine,validate}_chain and jtag_tap_{init,free} functions
- Added myself to the copyright header in both of these files.
- Used 'svn cp' to add files, so versioning was preserved for both.

git-svn-id: svn://svn.berlios.de/openocd/trunk@2149 b42882b7-edfa-0310-969c-e2dbd0fdcd60