member profile latest update inconsistency between page refresh/ajax load

[DJPaul]

The latest update as displayed on members' profiles is of inconsistent length, when you post a long string which gets truncated, between a page refresh and the initial content returned by the AJAX call.

[boonebgorges]

The JS that updates the header takes the update content directly from the AJAX response (which truncates to 358 characters), while on refresh it comes from bp_activity_latest_update() (which truncates to 180). Ideally, I'd be able to modify the JS to obey the 180 number. But because our AJAX handler bp_dtheme_post_update() returns HTML rather than structured data, this is nigh impossible. I either write a JS-equivalent of bp_create_excerpt(), or I rewrite the activity posting to return JSON data and then build the HTML in JS, or I make another AJAX call to get the shorter excerpt. All three of these options seem lousy, so I'm just going to change the default in bp_activity_latest_update().

[boonebgorges]

(In [4340]) Modifies default length of activity update in member header, to match what is returned by AJAX. Fixes #3203