Fix compiler warnings (-Wimplicit-fallthrough)

gcc warnings:

    src/ccmain/docqual.cpp:734:26: warning: this statement may fall through [-Wimplicit-fallthrough=]
    src/ccmain/docqual.cpp:764:26: warning: this statement may fall through [-Wimplicit-fallthrough=]
    src/ccmain/docqual.cpp:782:26: warning: this statement may fall through [-Wimplicit-fallthrough=]
    [...]

Signed-off-by: Stefan Weil <sw@weilnetz.de>

Author: stweil

src/ccmain/docqual.cpp

@@ -732,6 +732,7 @@ GARBAGE_LEVEL Tesseract::garbage_word(WERD_RES *word, BOOL8 ok_dict_word) {
           break;
         case FIRST_NUM:
           isolated_digits++;
+          // Fall through.
         default:
           state = FIRST_UPPER;
           last_char = word->uch_set->unichar_to_id(str, *lengths);
@@ -762,6 +763,7 @@ GARBAGE_LEVEL Tesseract::garbage_word(WERD_RES *word, BOOL8 ok_dict_word) {
           break;
         case FIRST_NUM:
           isolated_digits++;
+          // Fall through.
         default:
           state = FIRST_LOWER;
           last_char = word->uch_set->unichar_to_id(str, *lengths);
@@ -780,6 +782,7 @@ GARBAGE_LEVEL Tesseract::garbage_word(WERD_RES *word, BOOL8 ok_dict_word) {
         case FIRST_UPPER:
         case FIRST_LOWER:
           isolated_alphas++;
+          // Fall through.
         default:
           state = FIRST_NUM;
           break;

src/ccmain/resultiterator.cpp

@@ -452,6 +452,7 @@ bool ResultIterator::Next(PageIteratorLevel level) {
       }
       level = RIL_WORD;  // we've fallen through to the next word.
     }
+      // Fall through.
     case RIL_WORD:  // explicit fall-through.
     {
       if (it_->word() == nullptr) return Next(RIL_BLOCK);

src/ccutil/unichar.cpp

@@ -110,12 +110,15 @@ int UNICHAR::first_uni() const {
   case 4:
     uni += static_cast<unsigned char>(*src++);
     uni <<= 6;
+    // Fall through.
   case 3:
     uni += static_cast<unsigned char>(*src++);
     uni <<= 6;
+    // Fall through.
   case 2:
     uni += static_cast<unsigned char>(*src++);
     uni <<= 6;
+    // Fall through.
   case 1:
     uni += static_cast<unsigned char>(*src++);
   }