Change the handling of the debug break stack guard. The debug break is no longer ignored when hit inside "system" JavaScript. The reason for this is twofold:

* Running "system" JavaScript with the debug break flag active leads to slow running code while waiting for the break in non "system" JavaScript (one exception to this it is to try to avoid breaks in the clear mirror cache JavaScript code called when leaving the debugger).

* If this happens while processing RegExp running in native code an infinite loop is created as the stack guard handler for RegExp does not move execution forward

Fixed a GC bug in the interrupt handling for RegExp running in native code.

Added test of debug break while in debug message handler callback and debug break while executing a RegExp.
Review URL: http://codereview.chromium.org/115262

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2074 ce2b1a6d-e550-0410-aec6-3dcde31c8c00