Increase allowed size of a back-trace to 500 frames.
This limit is large enough for all practical purposes. It exists
only to sanity check the value specified with --num-callers.
Be frugal in record_ExeContext_wrk and only allocate on the stack 
as many frames as needed. 
Testcase included.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@12685 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/NEWS b/NEWS
index 73f8e6e..dbf3619 100644
--- a/NEWS
+++ b/NEWS
@@ -64,6 +64,8 @@
   rather than float values, as the shadow values are mostly
   used as bit patterns.
 
+* Increased limit for the --num-callers command line flag to 500.
+
 * ==================== FIXED BUGS ====================
 
 The following bugs have been fixed or resolved.  Note that "n-i-bz"