ubsan: runtime error: left shift of 249 by 24 places

pixman-bits-image.c:309:20: runtime error: left shift of 249 by 24 places cannot be represented in type 'int'

Change-Id: I4f67752f7826225cd2175198084a29ac248b873f
Reviewed-on: https://gerrit.libreoffice.org/45226Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

external/cairo/pixman/pixman-ubsan.patch

@@ -20,3 +20,14 @@
  
      next:
  	vx += ux;
+--- misc/pixman/pixman/pixman-bits-image.c
++++ misc/build/pixman/pixman/pixman-bits-image.c
+@@ -306,7 +306,7 @@
+     sgtot = CLIP (sgtot, 0, 0xff);
+     sbtot = CLIP (sbtot, 0, 0xff);
+ 
+-    return ((satot << 24) | (srtot << 16) | (sgtot <<  8) | (sbtot));
++    return (((uint32_t)satot << 24) | (srtot << 16) | (sgtot <<  8) | (sbtot));
+ }
+ 
+ static force_inline uint32_t