support: Introduce new subdirectory for test infrastructure

The new test driver in <support/test-driver.c> has feature parity with
the old one.  The main difference is that its hooking mechanism is
based on functions and function pointers instead of macros.  This
commit also implements a new environment variable, TEST_COREDUMPS,
which disables the code which disables coredumps (that is, it enables
them if the invocation environment has not disabled them).

<test-skeleton.c> defines wrapper functions so that it is possible to
use existing macros with the new-style hook functionality.

This commit changes only a few test cases to the new test driver, to
make sure that it works as expected.

support/test-driver.h

@@ -0,0 +1,68 @@
+/* Interfaces for the test driver.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_TEST_DRIVER_H
+#define SUPPORT_TEST_DRIVER_H
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+struct test_config
+{
+  void (*prepare_function) (int argc, char **argv);
+  int (*test_function) (void);
+  int (*test_function_argv) (int argc, char **argv);
+  void (*cleanup_function) (void);
+  void (*cmdline_function) (int);
+  const void *options;   /* Custom options if not NULL.  */
+  int timeout;           /* Test timeout in seconds.  */
+  int expected_status;   /* Expected exit status.  */
+  int expected_signal;   /* If non-zero, expect termination by signal.  */
+  char no_mallopt;       /* Boolean flag to disable mallopt.  */
+};
+
+enum
+  {
+    /* Test exit status which indicates that the feature is
+       unsupported. */
+    EXIT_UNSUPPORTED = 77,
+
+    /* Default timeout is twenty seconds.  Tests should normally
+       complete faster than this, but if they don't, that's abnormal
+       (a bug) anyways.  */
+    DEFAULT_TIMEOUT = 20,
+
+    /* Used for command line argument parsing.  */
+    OPT_DIRECT = 1000,
+    OPT_TESTDIR,
+  };
+
+/* Options provided by the test driver.  */
+#define TEST_DEFAULT_OPTIONS                            \
+  { "direct", no_argument, NULL, OPT_DIRECT },          \
+  { "test-dir", required_argument, NULL, OPT_TESTDIR }, \
+
+/* The directory the test should use for temporary files.  */
+extern const char *test_dir;
+
+int support_test_main (int argc, char **argv, const struct test_config *);
+
+__END_DECLS
+
+#endif /* SUPPORT_TEST_DRIVER_H */