[LyX/master] Fix a regression reported at #9146

[Scott Kostyshak]

commit ab67ce3757d76ab4df718f3f085b42420922e480
Author: Scott Kostyshak <skost...@lyx.org>
Date:   Wed Jun 4 13:52:42 2014 -0400

    Fix a regression reported at #9146
    
    This regression was introduced by me at 8b66f9ce. I did not take
    into account that a call to a python script containing $$s is embedded
    within a separate python script. Thus, when commandPrep() is called it
    only sees the call to the outer python script, and does not see the
    $$s contained in that python script. It therefore did not substitute
    for it. This fix simply calls commandPrep() directly before writing
    the embedded command.

diff --git a/src/graphics/GraphicsConverter.cpp 
b/src/graphics/GraphicsConverter.cpp
index 98580bd..263c91e 100644
--- a/src/graphics/GraphicsConverter.cpp
+++ b/src/graphics/GraphicsConverter.cpp
@@ -324,7 +324,7 @@ static void build_script(string const & from_file,
 
                ostringstream os;
                os << os::python() << ' '
-                  << "$$s/scripts/convertDefault.py" << ' ';
+                  << commandPrep("$$s/scripts/convertDefault.py") << ' ';
                if (!from_format.empty())
                        os << strip_digit(from_format) << ':';
                // The extra " quotes around infile and outfile are needed