Add missing function declarations to header

These two functions had not being defined in the header yet:

    mlib_delete_playlist()
    mlib_find_path()

Signed-off-by: Alex Waterman <imNotListening@gmail.com>

Add function to header file

mlib_delete_playlist() never was added to the header.

Signed-off-by: Alex Waterman <imNotListening@gmail.com>
Add a simple regression framework for keeping MLib sane

The framework just runs a simple regression function list and
reports statistics on pass/fails.

Signed-off-by: Alex Waterman <imNotListening@gmail.com>