[LyX/master] Handle backslash in escape function.

[Juergen Spitzmueller]

commit ef387c81af1294a3b5e7f65c23b313c371224b33
Author: Juergen Spitzmueller <sp...@lyx.org>
Date:   Fri Jan 27 09:15:47 2017 +0100

    Handle backslash in escape function.
    
    Fixes: #4595.
    
    Candidate for stable
---
 src/support/lstrings.cpp |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/src/support/lstrings.cpp b/src/support/lstrings.cpp
index 99591d0..1e3d346 100644
--- a/src/support/lstrings.cpp
+++ b/src/support/lstrings.cpp
@@ -1180,7 +1180,8 @@ docstring const escape(docstring const & lab)
        for (size_t i = 0; i < lab.length(); ++i) {
                char_type c = lab[i];
                if (c >= 128 || c == '=' || c == '%' || c == '#' || c == '$'
-                   || c == '}' || c == '{' || c == ']' || c == '[' || c == 
'&') {
+                   || c == '}' || c == '{' || c == ']' || c == '[' || c == '&'
+                   || c == '\\') {
                        // Although char_type is a 32 bit type we know that
                        // UCS4 occupies only 21 bits, so we don't need to
                        // encode bigger values. Test for 2^24 because we