[LyX/master] Fix math macro plain text output

[Georg Baum]

commit 3d492529bfa024e4c75f1db505881cefd1163674
Author: Georg Baum <b...@lyx.org>
Date:   Sun Mar 15 17:47:38 2015 +0100

    Fix math macro plain text output
    
    Previously it was not thread safe, and the translation could be wrong.

diff --git a/src/mathed/MathMacroTemplate.cpp b/src/mathed/MathMacroTemplate.cpp
index 82538e8..485a060 100644
--- a/src/mathed/MathMacroTemplate.cpp
+++ b/src/mathed/MathMacroTemplate.cpp
@@ -1273,7 +1273,7 @@ docstring MathMacroTemplate::xhtml(XHTMLStream &, 
OutputParams const &) const
 int MathMacroTemplate::plaintext(odocstringstream & os,
                                 OutputParams const &, size_t) const
 {
-       static docstring const str = '[' + buffer().B_("math macro") + ']';
+       docstring const str = '[' + buffer().B_("math macro") + ']';
 
        os << str;
        return str.size();