Patches item #1729825 ready to go.

[Daniel J S. <dan...@ie...>]

I consolidated all help/history patches into one patch #1729825 and it is ready 
to go.  Give it a try.  I guess the following would be the improvements:

1) Help now resolves keywords individually as opposed to a whole line of text 
(i.e., things like "help se ter post" are understood).  The algorithm goes with 
most matching characters as the "winning" help line, and if there is a tie then 
it is the most number of whole matches.

2) History is much more robust to recursion detection.  I went with an algorithm 
that will complain if every a command off the history stack is run more than 
once in a series of history recalls.  For example

plot x; hist !plot
plot x; hist !plot

is recursive on the second implementation because it will come back to the same 
line.  This uses dynarray to keep track of the recalled history, which actually 
turns out to be less code.

3) History now has recall by number, e.g., "hist !123".  A bit tricky to 
implement given the shuffling behavior we have, but I think I've got it.  (No 
sense in numbering the stack if we can't recall by number.)

Note, as far as shuffling it would be easy to make an option for that.  I point 
this out because if someone is using recall by number, shuffling of the stack 
can cause a problem.

Dan