Rewrote exception callstack generation to use the backtrace() and

backtrace_symbols() code.  Implemented the -callStackSymbols method from
	10.5 using this.  For this to be enabled, the configure script will
	require a small modification, which Gregory will add later.



git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/base/trunk@28662 72102866-910b-0410-8b05-ffd578937521

Headers/Foundation/NSException.h

@@ -123,6 +123,13 @@ extern "C" {
  * this value.
  */
 - (NSArray*) callStackReturnAddresses;
+/**
+ * Returns an array of the symbolic names of the call stack return addresses.  
+ * Note that, on some platforms, symbols are only exported in
+ * position-independent code and so these may only return numeric addresses for
+ * code in static libraries or the main application.  
+ */
+- (NSArray *)callStackSymbols;
 #endif
 
 /**