Rewrite libbacktrace using C++.

The old code was essentially trying to be C++ in C and was awkward. This
change makes it all objects with a thin layer that C code can use.

There is a C++ backtrace object that is not very useful, this code will
replace it.

This change also includes moving the backtrace test to a gtest, and adding
coverage of all major functionality.

Bug: 8410085
Change-Id: Iae0f1b09b3dd60395f71ed66010c1ea5cdd37841
diff --git a/libbacktrace/thread_utils.h b/libbacktrace/thread_utils.h
new file mode 100644
index 0000000..ae4c929
--- /dev/null
+++ b/libbacktrace/thread_utils.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _LIBBACKTRACE_THREAD_UTILS_H
+#define _LIBBACKTRACE_THREAD_UTILS_H
+
+#include <unistd.h>
+
+__BEGIN_DECLS
+
+int tgkill(int tgid, int tid, int sig);
+
+pid_t gettid();
+
+__END_DECLS
+
+#endif /* _LIBBACKTRACE_THREAD_UTILS_H */