simplify and unconfuse target_run_algorithm()

simplify and unconfuse target_run_algorithm()

For some reason there are *two* schemes for interposing logic into
the run_algorithm() code path...  One is a standard procedural wapper
around the target method invocation.

the other (superfluous) one hacked the method table by splicing
a second procedural wrapper into the method table.  Remove it:

	* Rename its  slightly-more-featureful wrapper so it becomes
	  the standard procedural wrapper, leaving its added logic
	  (where it should have been in the first place.

          Also add a paranoia check, to report targets that don't
	  support algorithms without traversing a NULL pointer, and
	  tweak its code structure a bit so it's easier to modify.

	* Get rid of the superfluous/conusing method table hacks.

This is a net simplification, making it simpler to analyse what's
going on, and then interpose logic . ... by ensuring there's only one
natural place for it to live.

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Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>