coverity#705164 Missing break in switch, assuming its intentional

Change-Id: I5cc112d7eb367f5dfe17fc39e3ef47784ae67e9b

filter/source/graphicfilter/ipbm/ipbm.cxx

@@ -170,6 +170,7 @@ bool PBMReader::ImplReadHeader()
     {
         case '1' :
             mbRaw = false;
+            //fall-through
         case '4' :
             mnMode = 0;
             nMax = 2;               // number of parameters in Header
@@ -177,12 +178,14 @@ bool PBMReader::ImplReadHeader()
             break;
         case '2' :
             mbRaw = false;
+            //fall-through
         case '5' :
             mnMode = 1;
             nMax = 3;
             break;
         case '3' :
             mbRaw = false;
+            //fall-through
         case '6' :
             mnMode = 2;
             nMax = 3;