Cleanup up stacktrace code

Updated qsort source from glibc.
Add debugging of keycache when EXTRA_DEBUG is specified

sql/stacktrace.h

@@ -0,0 +1,51 @@
+/* Copyright (C) 2000 MySQL AB
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+#ifdef HAVE_LINUXTHREADS
+#if defined(HAVE_STACKTRACE) || (defined (__i386__) || (defined(__alpha__) && defined(__GNUC__)))
+#undef HAVE_STACKTRACE
+#define HAVE_STACKTRACE
+
+extern char* __bss_start;
+extern char* heap_start;
+
+#define init_stacktrace() { heap_start = (char*) &__bss_start; }
+void print_stacktrace(gptr stack_bottom, ulong thread_stack);
+void safe_print_str(const char* name, const char* val, int max_len);
+#endif /* (defined (__i386__) || (defined(__alpha__) && defined(__GNUC__))) */
+
+#define HAVE_WRITE_CORE
+void write_core(int sig);
+#endif /* HAVE_LINUXTHREADS */
+
+/* Define empty prototypes for functions that are not implemented */
+#ifndef HAVE_STACKTRACE
+#define init_stacktrace() {}
+#define print_stacktrace(A,B) {}
+#define safe_print_str(A,B,C) {}
+#endif /* HAVE_STACKTRACE */
+
+#ifndef HAVE_WRITE_CORE
+#define write_core(A) {}
+#endif
+
+#ifdef	__cplusplus
+}
+#endif