ignore buffer overflow in magick

for lsan testing

.travis.yml

@@ -69,7 +69,7 @@ addons:
   apt:
     update: true
     sources:
-      # use imagemagick 6.9.7-4 instead of 6.8.9-9 
+      # use a more recent imagemagick instead of 6.8.9-9 
       - sourceline: 'ppa:opencpu/imagemagick'
       # add support for HEIF files
       - sourceline: 'ppa:strukturag/libheif'

lsan.supp

@@ -3,3 +3,4 @@ leak:libfontconfig.so
 leak:libglib-2.0.so
 leak:libIlmImf-2_2.so
 leak:libstdc++.so
+heap-buffer-overflow:libMagickCore-6.Q16.so