Use the libbacktrace C++ interface instead of the C interface in debuggerd.
Reformat the debuggerd code to be closer to Google C++ style.
Fix all debuggerd casts to be C++ casts.
Add a frame number to the frame data structure for ease of formatting and
add another FormatFrameData function.
Change the format_test to use the new FormatFrameData function.
Modify all of the backtrace_test to use the C++ interface.
Change-Id: I10e1610861acf7f4a3ad53276b74971cfbfda464