Make sure that the constructors in SVN class makes a proper cleanup in cases of abort.

[Jari Häkkinen]

error stuff must be clean up manually, from svn API docs:

[Jari Häkkinen]

error stuff must be clean up manually, from svn API docs:

void svn_error_clear(svn_error_t *error)

Free the memory used by error, as well as all ancestors and descendants of error.

Unlike other Subversion objects, errors are managed explicitly; you MUST clear an error if you are ignoring it, or you are leaking memory. For convenience, error may be NULL, in which case this function does nothing; thus, svn_error_clear(svn_foo(...)) works as an idiom to ignore errors.

[Jari Häkkinen]

(In [91]) Fixes #4, #19, #32, #34: Started to implement subversion API usage.