check for polyglossia alongside babel

[jamieforth]

This is in relation to file names and active double quotes.

svg produces an Undefined control sequence error when using xelatex and polyglossia (i.e. not babel).

This patch adds support for polyglossia alongside babel. However, the fix only works for languages that support babel shorthands, because only those languages load babelsh.def, in which \bbl@deactivate is defined.

\documentclass{article}

\usepackage{svg}

\usepackage{polyglossia}
% Languages that load babelsh.def (e.g. Dutch) work because 
% \bbl@deactivate is defined in that file.
\setmainlanguage[babelshorthands]{dutch}

% Other languages that do not load babelsh.def (e.g. English)
% still result in \bbl@deactivate undefined.
% \setmainlanguage[babelshorthands]{english}

\begin{document}
\includesvg{./figure.svg}
\end{document}

ERROR: Undefined control sequence.

--- TeX said ---
\svg@deactivate@dq ->\bbl@deactivate 
                                     {"}
l.595 }

[mrpiggi]

solved with 9091990