[LyX/2.0.x] Add comment.

[Richard Heck]

commit a9f9c1bc6e9a3f53d2c0ab50cd8f50a7878432f1
Author: Richard Heck <rgh...@lyx.org>
Date:   Fri Jan 24 12:41:22 2014 -0500

    Add comment.

diff --git a/src/insets/InsetSpace.cpp b/src/insets/InsetSpace.cpp
index 6e7c94d..179588f 100644
--- a/src/insets/InsetSpace.cpp
+++ b/src/insets/InsetSpace.cpp
@@ -691,6 +691,7 @@ docstring InsetSpace::xhtml(XHTMLStream & xs, OutputParams 
const &) const
                break;
        case InsetSpaceParams::QQUAD:
                output ="&emsp;";
+               // fall through. the qquad is two spaces thick.
        case InsetSpaceParams::THICK:
        case InsetSpaceParams::QUAD:
                output ="&emsp;";