Add main() test methods to reduce test boilerplate.

Simple tests only need to implement register_tests().
Tests that need a custom main() should implement test_main(). This will
be wrapped in a main() that performs common setup/teardown (currently
crypto-mdebug).

Note that for normal development, enable-asan is usually
sufficient for detecting leaks, and more versatile.

enable-crypto-mdebug is stricter as it will also
insist that all static variables be freed. This is useful for debugging
library init/deinit; however, it also means that test_main() must free
everything it allocates.

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
diff --git a/test/test_main_custom.h b/test/test_main_custom.h
new file mode 100644
index 0000000..22bc8f5
--- /dev/null
+++ b/test/test_main_custom.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the OpenSSL license (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#ifndef HEADER_TEST_MAIN_CUSTOM_H
+# define HEADER_TEST_MAIN_CUSTOM_H
+
+/*
+ * Unit tests that need a custom main() should implement test_main and link to
+ * test_main_custom.c
+ * test_main() should return the result of run_tests().
+ */
+extern int test_main(int argc, char *argv[]);
+
+#endif  /* HEADER_TEST_MAIN_CUSTOM_H */