[LyX/master] Add comments to fix coverity #23505 and 23507.

[Richard Heck]

commit e622f82521e818ca961f82599ff2b1c084676b8e
Author: Richard Heck <rgh...@lyx.org>
Date:   Sun Jun 12 00:34:35 2016 -0400

    Add comments to fix coverity #23505 and 23507.

diff --git a/src/insets/InsetListingsParams.cpp 
b/src/insets/InsetListingsParams.cpp
index d365d89..f375661 100644
--- a/src/insets/InsetListingsParams.cpp
+++ b/src/insets/InsetListingsParams.cpp
@@ -223,6 +223,8 @@ docstring ListingsParam::validate(string const & par) const
                        return bformat(_("Try one of %1$s."), from_utf8(info_));
                else
                        return bformat(_("I guess you mean %1$s."), 
from_utf8(matching_names));
+               // this stifles a warning but upsets coverity
+               // coverity[UNREACHABLE]
                return docstring();
        }
        case SUBSETOF:
@@ -685,6 +687,8 @@ docstring ParValidator::validate(string const & name,
                        return bformat(_("Parameters starting with '%1$s': 
%2$s"),
                                                                
from_utf8(name), from_utf8(matching_names));
        }
+       // this stifles a warning but upsets coverity
+       // coverity[UNREACHABLE]
        return docstring();
 }