Debugger UI terminology

[Vladimir Prus]

Hello!
At the moment, the debugger UI uses "watch" in two different meanings.

- In the variables widget, there's "Watch" section. Expressions there
  are reevaluated after each step.

- The breakpoint widget, and the popup menu in the variables widget, uses
  "Watchpoint" -- that is "breakpoint on value change"

I think that those two meaning might well confuse users, especially when they 
appear in the same popup menu:

   http://zigzag.cs.msu.su/~ghost/variables_popup_new.png
   
There's both "Watch variable" and "Toggle watchpoint" items.

I think that even renaming "Toggle watchpoint" to "Toggle breakpoint" will be 
an improvement. Any comments?

- Volodya