-Werror=implicit-fallthrough= (GCC 7)

Change-Id: I9d6c7e5a03aea56d8db84c2ba06c63efb0e007fa

rsc/source/rscpp/cpp1.c

@@ -278,6 +278,7 @@ int MAIN(int argc, char** argv)
                 }
             }                           /* Continue by opening output    */
         }
+        /* fall through */
 #endif
     case 3:
         /*
@@ -293,6 +294,7 @@ int MAIN(int argc, char** argv)
                 exit(IO_ERROR);
             }
         }                           /* Continue by opening input    */
+        /* fall through */
     case 2:                         /* One file -> stdin            */
         /*
          * Open input file, "-" means use stdin.
@@ -309,6 +311,7 @@ int MAIN(int argc, char** argv)
             strncpy(work, useargv[1], NWORK);  /* Remember input filename      */
             break;
         }                           /* Else, just get stdin         */
+        /* fall through */
     case 0:                         /* No args?                     */
     case 1:                         /* No files, stdin -> stdout    */
         work[0] = EOS;              /* Unix can't find stdin name   */

rsc/source/rscpp/cpp2.c

@@ -120,6 +120,7 @@ int control(int counter)
             if (++ifptr >= &ifstack[BLK_NEST])
                 goto if_nest_err;
             *ifptr = 0;                     /* !WAS_COMPILING       */
+            /* fall through */
         case L_line:                        /* Many                 */
             /*
              * Are pragma's always processed?

rsc/source/rscpp/cpp4.c

@@ -190,7 +190,7 @@ void dodefine()
                 break;                      /* spaces               */
             else if (c == '\t')
                 c = ' ';                    /* Normalize tabs       */
-            /* Fall through to store character                      */
+            /* fall through *//* to store character                 */
         default:                            /* Other character      */
             save(c);
             break;
@@ -461,6 +461,7 @@ void expand(DEFBUF* tokenp)
                 dumpparm("expand");
 #endif
         }                           /* Collect arguments            */
+        /* fall through */
     case DEF_NOARGS:                /* No parameters just stuffs    */
         expstuff(tokenp);           /* Do actual parameters         */
     }                               /* nargs switch                 */

rsc/source/rscpp/cpp5.c

@@ -352,6 +352,7 @@ again:
                        opname[(int)opp->op]);
                 return 1;
             }
+            /* fall through */
         /*
          * Evaluate op1.
          */

rsc/source/rscpp/cpp6.c

@@ -902,7 +902,7 @@ int get()
 #ifdef STRICT_COMMENTS
                     cwarn("Nested comments", NULLST);
 #endif
-                    /* Fall into * stuff    */
+                    /* fall through *//* into * stuff */
                 case '*':
                     if ((c = get()) != '/')     /* If comment doesn't   */
                         goto test;              /* end, look at next    */