There is a growing number of path concatenation cases, each built on
some memory allocation scheme and some variant of sprintf.
Introduce a pathbuf type and a few primitive operations to reset the
pathbuf, clone a pathbuf, push a path/filename to the pathbuf, get the
path, and truncate the path by dirname().
Also provide a convenient qdl_path_exist() operation to test if the
pathbuf refers to an existing file.
Signed-off-by: Bjorn Andersson <bjorn.andersson@oss.qualcomm.com>
