Add wrapper for libssh2_trace functions

[volks73]

The libssh2.org library provides the libssh2_trace() function to aid in debugging. This function is currently not available in this library, which makes it hard to debug and troubleshoot. A LabVIEW-friendly wrapper function should be added.

The default is to write debugging statements to STDERR. This can cause a problem with LabVIEW because there is no STDERR. In other words, I am not sure if the debugging statements will appear if tracing is turned on. Will a CMD console display automatically? Will the debugging statements only appear if LabVIEW is started from the command line (CMD)?

There is the libssh2_trace_sethandler which can be used to redirect the debugging output from STDERR to another location, like a buffer or log file. To truly implement the debugging facility a LabVIEW-friendly output will need to be implemented. Most likely a wrapper function that takes a path to a file and this library automatically creates the function pointer to pass to the libssh2 library.

Enabling debugging during the build of the library also needs to be enabled for the libssh2_trace to be available.