Bug#37003 Tests sporadically crashes with embedded server

The problem was that when a embedded linked version of mysqltest
crashed there was no way to obtain a stack trace if no core file
is available. Another problem is that the embedded version of
libmysql was not behaving (crash) the same as the non-embedded with
respect to sending commands to a explicitly closed connection.

The solution is to generate a mysqltest's stack trace on crash
and to enable "reconnect" if the connection handle was explicitly
closed so the behavior matches the non-embedded one.

client/CMakeLists.txt:
  Link mysys to mysqltest.
client/Makefile.am:
  Link mysys to mysqltest.
client/mysqltest.c:
  Add fatal signal handling with backtracing for Unix and Windows.
configure.in:
  Add check for weak symbols support and remove a spurious word.
include/Makefile.am:
  Add new header with prototype for stack tracing functions.
include/my_stacktrace.h:
  Add new header with prototype for stack tracing functions.
libmysqld/CMakeLists.txt:
  stack tracing is now part of mysys.
libmysqld/Makefile.am:
  stack tracing is now part of mysys.
libmysqld/lib_sql.cc:
  Re-connect if connection was explicitly closed. This is
  done to match the behavior of the non-embeded libmysql.
mysql-test/t/sql_low_priority_updates_func.test:
  Test expects parallelism between queries that cannot be
  guaranteed under embedded.
mysys/CMakeLists.txt:
  Add stacktrace to mysys.
mysys/Makefile.am:
  Add stacktrace to mysys.
mysys/stacktrace.c:
  Move stacktrace to mysys and add weak symbol for the
  C++ name de-mangling function so that it can later be
  overridden in C++ code. Also add my_ prefix to exported
  functions.
sql/CMakeLists.txt:
  stacktrace was moved to mysys.
sql/Makefile.am:
  stacktrace was moved to mysys.
sql/mysqld.cc:
  Add my_ prefix to mysys functions.

include/my_stacktrace.h

@@ -0,0 +1,61 @@
+/* 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; version 2 of the License.
+
+   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 */
+
+#ifndef _my_stacktrace_h_
+#define _my_stacktrace_h_
+
+#include <my_global.h>
+
+#ifdef TARGET_OS_LINUX
+#if defined (__x86_64__) || defined (__i386__) || \
+    (defined(__alpha__) && defined(__GNUC__))
+#define HAVE_STACKTRACE 1
+#endif
+#elif defined(__WIN__)
+#define HAVE_STACKTRACE 1
+#endif
+
+#if !defined(__NETWARE__)
+#define HAVE_WRITE_CORE
+#endif
+
+#if HAVE_BACKTRACE && HAVE_BACKTRACE_SYMBOLS && \
+    HAVE_CXXABI_H && HAVE_ABI_CXA_DEMANGLE && \
+    HAVE_WEAK_SYMBOL
+#define BACKTRACE_DEMANGLE 1
+#endif
+
+C_MODE_START
+
+#if defined(HAVE_STACKTRACE) || defined(HAVE_BACKTRACE)
+void my_init_stacktrace();
+void my_print_stacktrace(uchar* stack_bottom, ulong thread_stack);
+void my_safe_print_str(const char* name, const char* val, int max_len);
+void my_write_core(int sig);
+#if BACKTRACE_DEMANGLE
+char *my_demangle(const char *mangled_name, int *status);
+#endif
+#ifdef __WIN__
+void my_set_exception_pointers(EXCEPTION_POINTERS *ep);
+#endif
+#endif
+
+#ifdef HAVE_WRITE_CORE
+void my_write_core(int sig);
+#endif
+
+C_MODE_END
+
+#endif /* _my_stacktrace_h_ */