Use glibc backtrace functions instead of our own

Our own functions don't seem to work with the latest gcc,
so it seems to make sense to use the glibc versions which
should be equivalent and maintained.

lib/backtrace.c

@@ -38,6 +38,7 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include "compiler.h"
+#include <execinfo.h>
 
 #define THIS_MODULE VLM_backtrace
 #include "vlog.h"
@@ -106,8 +107,9 @@ in_stack(void *p)
 }
 
 void
-backtrace_capture(struct backtrace *backtrace)
+backtrace_capture(struct backtrace *bt)
 {
+#ifdef OLD_BACKTRACE_CAPTURE
     void **frame;
     size_t n;
 
@@ -117,7 +119,10 @@ backtrace_capture(struct backtrace *backtrace)
              && n < BACKTRACE_MAX_FRAMES;
          frame = frame[0])
     {
-        backtrace->frames[n++] = (uintptr_t) frame[1];
+        bt->frames[n++] = (uintptr_t) frame[1];
     }
-    backtrace->n_frames = n;
+    bt->n_frames = n;
+#else
+    bt->n_frames = backtrace(bt->frames, BACKTRACE_MAX_FRAMES);
+#endif
 }

lib/fault.c

@@ -40,6 +40,7 @@
 #include <string.h>
 #include <signal.h>
 #include "util.h"
+#include <execinfo.h>
 
 #include "vlog.h"
 #define THIS_MODULE VLM_fault
@@ -59,12 +60,13 @@ fault_handler(int sig_nr)
 void
 log_backtrace(void)
 {
+#define STACK_DEPTH_LIMIT	128
+#ifdef OLD_LOG_BACKTRACE
     /* During the loop:
 
        frame[0] points to the next frame.
        frame[1] points to the return address. */
     void **frame;
-#define STACK_DEPTH_LIMIT	128
     int stack_depth = 0;
     for (frame = __builtin_frame_address(0);
          frame != NULL && frame[0] != NULL
@@ -79,9 +81,17 @@ log_backtrace(void)
                     (char *) frame[1] - (char *) addrinfo.dli_saddr); 
         }
     }
+#else
+    /* Use glibc functions to print backtrace */
+    void *buffer[STACK_DEPTH_LIMIT];
+    backtrace(buffer, STACK_DEPTH_LIMIT);
+    backtrace_symbols_fd(buffer, STACK_DEPTH_LIMIT, fileno(stderr));
+#endif
     fflush(stderr);
 }
 
+
+
 void
 register_fault_handlers(void)
 {