Eliminates 'flash_cmd' global variable.

Changes the jtag_interface->register_callbacks field to a list of
commands to be registered.  Changes callback to invocation of
register_commands() with that command registration list.  Removes all
JTAG interface driver register_command callback functions, which the
previous commits had converted into identical calls.

Use register_commands() with command registration array.

Use register commands with command registration array.

Use register_commands() with command registration array.

Use register_commands() with a command registration array.

Use register_commands() with command registration array.

Use register_commands() with command registration array.

Use register_commands() with a command registration array.

Use register_commands() with command registration array.
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This module was broken by previous changes, but no one has complained.
Are there still users for this modules?

Uses register_commands() with command registration array.

Use register_commands() with command_registration array.

Remove register_callbacks from pld_device structure, using an array
of command_registration records instead.

Updates core PLD and virtex2 commands to use register_commands().

Use register_commands() for registering {,x}svf commands.

Converts server directory to use new command registration paradigm.

Use register_commands() for logging callbacks.  Improve help and add
proper usage.

Use table instead of individual calls.  Add proper usage information.

Use register_commands() for top-level version and init command.

Use the new command registration chaining capabilities to eliminate
the foo_register_commands helper, folding its remaining command
handler setup into the hello_command_handlers registration array.

Use new register_commands() with command registration table.

Rewrite the magical 'unknown' command in C as a Jim handler, allowing
it to dispatch commands to any level in the tree.

Allow other modules to find a command, primarily for the purpose of
registering and unregistering subcommands.

Move command context acquisition to current_command_context() for re-use.

Adds the ability to chain registration structures.  Modules can define a
command with the 'chain' and 'num_chain' fields defined in their
registration table, and the register_commands() function will initialize
these commands.  If the registration record creates a new command, then
the chained commands are created under it; otherwise, they are created
in the same context as the other commands (i.e. the parent argument).

Split out the handler registration into its own function, and add a
few obviously missing NULL pointer error checking.

Use register_commands() to register low-level command handlers,
adding a builtin_command_handlers declaration that is easy to understand.
Splits help and usage information into their appropriate fields.

Adds the usage command, to display usage information for commands.
The output for this command will remain erronenously empty until
commands are updated to use these new coventions.

The register_commands API takes multiple commands in one call, allowing
modules to declare and pass a much simpler (and more explicit) array of
command_registration records.

Add a structure to encapsulate command registration information, rather
than passing them all as parameters.  Enables further API changes that
require additional required or optional parameters.

Updates the register_command API and COMMAND_REGISTER macro to use it,
along with their documentation.

Replaces direct calls to register_command() with a macro, to allow
its parameters to be changed and callers updated in phases.

Provides a migration path for the widely used register_command API,
which needs to be updated to provide new functionality.

This macro allows the API to change without having to update all of its
callers at the same time.