avoid-slur not set

[Henrik Frisk]

Hello,

I've been away from the list for some time. Noticed
that convert-ly erroneously (?) changed my \epsfile markups in a file
version 2.7.15 to \\epsfile when updating it to 2.9.13. This is on the
OSX version.

****************
\version "2.7.15"

\new Staff \relative c' {
    c4^\markup {\epsfile #"nssffff.eps"}
}

****************

results in 

****************
\version "2.9.11"

\new Staff \relative c' {
    c4^\markup {\\epsfile #X #10 #"nssffff.eps"}
}
****************

/henrik