chore: ci_is_equal slow path is fixed

src/grammar/ci_string.cpp

@@ -40,14 +40,14 @@ ci_is_equal(
             goto slow;
     }
     return true;
-slow:
     do
     {
+        a = *p1++;
+        b = *p2++;
+    slow:
         if( to_lower(a) !=
             to_lower(b))
             return false;
-        a = *p1++;
-        b = *p2++;
     }
     while(n--);
     return true;

test/unit/grammar/ci_string.cpp

@@ -88,6 +88,9 @@ public:
 
         BOOST_TEST(ci_equal{}("abc", "ABC"));
         BOOST_TEST(! ci_equal{}("xz", "abc"));
+
+        // slow case
+        BOOST_TEST(ci_is_equal("/x", "/X"));
     }
 
     void