export-latex option is not applied when it is in a directory

[Donghyeon Lee]

I'd ran `inkscape -D -z --file=foobar.svg --export-pdf=figures/foobar.pdf --export-latex` to extract .pdf and .pdf_tex files from .svg.
It works with no errors.
But when I import the `foobar.pdf_tex` in `figures` directory, using following,

\begin{figure}
    \centering
    \def\svgwidth{\columnwidth}
    \input{figures/foobar.pdf_tex}
\end{figure}

... it occurs annoying errors such as following:

LaTeX Warning: File `foobar.pdf' not found on input line 52.

! Package pdftex.def Error: File `foobar.pdf' not found.

See the pdftex.def package documentation for explanation.
Type H <return> for immediate help.
 ...

l.52 ...h,page=1]{foobar.pdf}}
                        %
Using draft setting for this image.
Try typing <return> to proceed.
If that doesn't work, type X <return> to quit.

I think the errors was occurred because the `--export-pdf` option that specified a directory isn't applied.

See a part of `foobar.pdf_tex`:

    \put(0,0){\includegraphics[width=\unitlength,page=1]{foobar.pdf}}%

I'd edit this row as following, it works fine in LaTeX also:

    \put(0,0){\includegraphics[width=\unitlength,page=1]{figures/foobar.pdf}}%

[Donghyeon Lee (leedh)]

I wrote simple patcher for this: https://gist.github.com/leedh/6ac029b2e1aee72889ef3dcf639ab62e