New features
------------

- Syntactic filtering: control whether to match in comments, strings, 
and normal text.

- Symbol search: like word search, but looks only at symbol boundaries

- One ring: optionally share a search ring between normal and regular 
expression searches. The additional history storage described below 
allows this mode to work reliably.

Bugfixes
--------

- After an isearch settings change, we refresh the state stored at the 
to of the stack. This way, we don't lose track of settings after adding 
characters to the search string and removing them again.

The patch also changes some behavior:

- With the patch, we store isearch state in the history ring alongside 
the actual search strings.  This information allows us to exactly 
recreate searches when we pull them from history.

Other behavior changes
----------------------

- Case sensitivity is now displayed alongside other isearch settings in 
the isearch prompt.  Previously, the only indication we gave of case 
sensitivity was a fleeing message displayed briefly each time the user 
toggled the setting.

- isearch no longer prints "pending". I don't see why this message would 
be useful.