[LyX/master] Autodetect the EMF format

[Enrico Forestieri]

commit db9c8c6d0229eccdcc28d55eead018d9e40347a4
Author: Enrico Forestieri <for...@lyx.org>
Date:   Wed Jul 4 19:52:13 2018 +0200

    Autodetect the EMF format
    
    Otherwise it will be recognized only by the file extension, because
    libmagic returns "application/octet-stream" as mime type. Moreover,
    if the emf encapsulates a binary image format, it can be confused
    with this other format and its preview on screen fails.
---
 src/Format.cpp |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/src/Format.cpp b/src/Format.cpp
index a4882f6..ab09d4a 100644
--- a/src/Format.cpp
+++ b/src/Format.cpp
@@ -337,6 +337,9 @@ string guessFormatFromContents(FileName const & fn)
                        // autodetect pdf format for graphics inclusion
                        format = "pdf6";
 
+               else if (contains(str, " EMF"))
+                       format = "emf";
+
                else if (contains(str, "PNG"))
                        format = "png";